good enough!

Content.Client/Chemistry/UI/ChemMasterBoundUserInterface.cs

@@ -50,6 +50,7 @@ protected override void Open()
             _window.OnReagentButtonPressed += (_, button, amount, isOutput) => SendMessage(new ChemMasterReagentAmountButtonMessage(button.Id, amount, button.IsBuffer, isOutput));
             _window.OnSortMethodChanged += sortMethod => SendMessage(new ChemMasterSortMethodUpdated(sortMethod));
             _window.OnTransferAmountChanged += amount => SendMessage(new ChemMasterTransferringAmountUpdated(amount));
+            _window.OnUpdateAmounts += amounts => SendMessage(new ChemMasterAmountsUpdated(amounts));
         }
 
         /// <summary>

Content.Client/Chemistry/UI/ChemMasterWindow.xaml

@@ -137,12 +137,18 @@
             </PanelContainer>
             <RichTextLabel Name="AmountLabel" Text="{Loc 'chem-master-window-transferring-default-label'}"  Margin="0 0 7 0" />
             <LineEdit MinSize="140 0" Name="AmountLineEdit" Access="Public" PlaceHolder="{Loc 'chem-master-window-amount-placeholder'}" />
+            <BoxContainer Orientation="Horizontal" HorizontalExpand="True">
+                <Button Name="SetAmountButton" Text="{Loc 'chem-master-window-set-amount-label'}" HorizontalExpand="True" StyleClasses="OpenRight"/>
+                <Button Name="SaveAsFrequentButton" Text="{Loc 'chem-master-window-save-as-frequent-label'}" HorizontalExpand="True" StyleClasses="OpenLeft"/>
+            </BoxContainer>
+            <Label Text="Both of the above buttons use the textbox" />
+            <Control MinSize="0 5" />
             <GridContainer
                 Name="AmountButtons"
                 VerticalExpand="True"
                 HorizontalExpand="True"
                 Margin="2 2 2 2"
-                Columns="5" />
+                Columns="4" />
         </BoxContainer>
     </BoxContainer>
 </controls:FancyWindow>

Content.Client/Chemistry/UI/ChemMasterWindow.xaml.cs

@@ -28,8 +28,12 @@ public sealed partial class ChemMasterWindow : FancyWindow
         public event Action<int>? OnAmountButtonPressed;
         public event Action<int>? OnSortMethodChanged;
         public event Action<int>? OnTransferAmountChanged;
+        public event Action<List<int>>? OnUpdateAmounts;
+
         public readonly Button[] PillTypeButtons;
 
+        private List<int> _amounts = new();
+
         private const string TransferringAmountColor = "#ffffff";
         private ReagentSortMethod _currentSortMethod = ReagentSortMethod.Alphabetical;
         private ChemMasterBoundUserInterfaceState? _lastState;
@@ -48,7 +52,9 @@ public ChemMasterWindow()
 
             AmountLabel.HorizontalAlignment = HAlignment.Center;
             AmountLineEdit.OnTextEntered += SetAmount;
-            AmountLineEdit.OnFocusExit += SetAmount;
+
+            SetAmountButton.OnPressed += _ => SetAmountText(AmountLineEdit.Text);
+            SaveAsFrequentButton.OnPressed += HandleSaveAsFrequentPressed;
 
             // Pill type selection buttons, in total there are 20 pills.
             // Pill rsi file should have states named as pill1, pill2, and so on.
@@ -130,15 +136,19 @@ public ChemMasterWindow()
             BufferTransferButton.OnPressed += HandleDiscardTransferPress;
             BufferDiscardButton.OnPressed += HandleDiscardTransferPress;
 
-            var amounts = new List<int>()
-            {
-                1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, 200, 225, 250, 275, 300, 500
-            };
+            CreateAmountButtons();
+
+            OnAmountButtonPressed += amount => SetAmountText(amount.ToString());
+        }
+
+        private void CreateAmountButtons()
+        {
+            AmountButtons.DisposeAllChildren();
 
-            for (int i = 0; i < amounts.Count; i++)
+            for (int i = 0; i < _amounts.Count; i++)
             {
                 var styleClass = StyleBase.ButtonOpenBoth;
-                var amount = amounts[i];
+                var amount = _amounts[i];
                 var columns = AmountButtons.Columns;
 
                 if (i == 0 || i % columns == 0)
@@ -158,8 +168,17 @@ public ChemMasterWindow()
                 button.OnPressed += _ => OnAmountButtonPressed?.Invoke(amount);
                 AmountButtons.AddChild(button);
             }
+        }
 
-            OnAmountButtonPressed += amount => SetAmountText(amount.ToString());
+        private void HandleSaveAsFrequentPressed(BaseButton.ButtonEventArgs args)
+        {
+            if (!int.TryParse(AmountLineEdit.Text, out var amount)
+                || _amounts.Any(a => amount == a))
+                return;
+
+            _amounts.Add(amount);
+            _amounts.Sort();
+            CreateAmountButtons();
         }
 
         private void HandleDiscardTransferPress(BaseButton.ButtonEventArgs args)
@@ -276,6 +295,13 @@ public void UpdateState(BoundUserInterfaceState state)
             HandleSortMethodChange(castState.SortMethod);
             SetAmountText(castState.TransferringAmount.ToString());
 
+            if (_amounts != castState.Amounts)
+            {
+                _amounts = castState.Amounts;
+                _amounts.Sort();
+                CreateAmountButtons();
+            }
+
             BufferCurrentVolume.Text = $" {castState.PillBufferCurrentVolume?.Int() ?? 0}u";
 
             InputEjectButton.Disabled = castState.ContainerInfo is null;

Content.Server/Chemistry/Components/ChemMasterComponent.cs

@@ -28,6 +28,12 @@ public sealed partial class ChemMasterComponent : Component
         public int SortMethod;
 
         [DataField]
-        public int TransferringAmount;
+        public int TransferringAmount = 1;
+
+        [DataField]
+        public List<int> Amounts = new()
+        {
+            1, 5, 10, 15, 20, 25, 30, 50
+        };
     }
 }

Content.Server/Chemistry/EntitySystems/ChemMasterSystem.cs

@@ -64,8 +64,12 @@ public override void Initialize()
             SubscribeLocalEvent<ChemMasterComponent, ChemMasterOutputToBottleMessage>(OnOutputToBottleMessage);
             SubscribeLocalEvent<ChemMasterComponent, ChemMasterSortMethodUpdated>(OnSortMethodUpdated);
             SubscribeLocalEvent<ChemMasterComponent, ChemMasterTransferringAmountUpdated>(OnTransferringAmountUpdated);
+            SubscribeLocalEvent<ChemMasterComponent, ChemMasterAmountsUpdated>(OnAmountsUpdated);
         }
 
+        private void OnAmountsUpdated(Entity<ChemMasterComponent> ent, ref ChemMasterAmountsUpdated args) =>
+            ent.Comp.Amounts = args.Amounts;
+
         private void SubscribeUpdateUiState<T>(Entity<ChemMasterComponent> ent, ref T ev) =>
             UpdateUiState(ent);
 
@@ -97,7 +101,8 @@ private void UpdateUiState(Entity<ChemMasterComponent> ent, bool updateLabel = f
                 chemMaster.PillDosageLimit,
                 updateLabel,
                 chemMaster.SortMethod,
-                chemMaster.TransferringAmount);
+                chemMaster.TransferringAmount,
+                chemMaster.Amounts);
 
             _userInterfaceSystem.SetUiState(owner, ChemMasterUiKey.Key, state);
         }

Content.Shared/Chemistry/SharedChemMaster.cs

@@ -98,6 +98,12 @@ public sealed class ChemMasterTransferringAmountUpdated(int transferringAmount)
         public readonly int TransferringAmount = transferringAmount;
     }
 
+    [Serializable, NetSerializable]
+    public sealed class ChemMasterAmountsUpdated(List<int> amounts) : BoundUserInterfaceMessage
+    {
+        public readonly List<int> Amounts = amounts;
+    }
+
     public enum ChemMasterMode
     {
         Transfer,
@@ -152,7 +158,8 @@ public sealed class ChemMasterBoundUserInterfaceState(
         uint pillDosageLimit,
         bool updateLabel,
         int sortMethod,
-        int transferringAmount)
+        int transferringAmount,
+        List<int> amounts)
         : BoundUserInterfaceState
     {
         public readonly ContainerInfo? ContainerInfo = containerInfo;
@@ -179,6 +186,8 @@ public sealed class ChemMasterBoundUserInterfaceState(
 
         public readonly int SortMethod = sortMethod;
         public readonly int TransferringAmount = transferringAmount;
+
+        public readonly List<int> Amounts = amounts;
     }
 
     [Serializable, NetSerializable]

Resources/Locale/en-US/chemistry/components/chem-master-component.ftl

@@ -23,6 +23,8 @@ chem-master-window-pill-buffer-text = Pill Buffer
 chem-master-window-pill-buffer-label = pill buffer:
 chem-master-window-pill-buffer-empty-text = Pill buffer empty.
 chem-master-window-pill-buffer-low-text = Not enough solution in pill buffer
+chem-master-window-save-as-frequent-label = Save as Frequent
+chem-master-window-set-amount-label = Set Amount
 chem-master-window-transfer-button = Transfer
 chem-master-window-sort-method-tooltip = Choose your buffer's sort method.
 chem-master-window-sort-method-Time-text = Last Added