Is there existing plugin or functionality for a hovering "add block"?

[jordie23]

Before I go and try to attempt to build this out, I'm wondering if there's any existing plugin that has this (or similar) functionality?

Basically when using SlateJS editor, the goal would be to have a "add block" button appear between existing blocks when the mouse is hovered near. (or to the left) When clicked they can select a block type and it will be inserted in that location.

Example from wordpress:

Example from editor.js:

Does anyone know if something like this exists anywhere in a plugin or code sample? I think plate has a draggable handle that appears on hover, but I couldn't see an "add block" part.