Side menu "Add block" (+) not usable with keyboard (hover-only, Tab captured, Enter/Space)

Start by locating the side-menu implementation, especially SideMenu.Button and the editor's Tab keyboard handling. Reproduce the issue using only caret movement, Tab, Enter, and Space without hovering. Done means the side menu appears for the focused block, remains reachable by keyboard, and its buttons open the expected menu through keyboard and screen-reader interaction.

Discussed in https://github.com/TypeCellOS/BlockNote/discussions/2577

^{Originally posted by Ovgodd March 20, 2026}

What’s broken?

Problem

The “Add block” (+) and the 6 dots optionbutton in the left margin:

• Mostly appears on mouse hover : little or no access with keyboard only.
• Tab rarely reaches it: the editor captures Tab for indenting blocks, with no exception for the side menu
• Enter / Space often don’t open the insert menu when the handler is on the icon instead of the actual button.

What did you expect to happen?

The + button should appear and be reachable without mouse hover, Tab should focus it when the side menu is visible, and Enter/Space should open the insert menu like a click, including with a screen reader.

Steps to reproduce

1. Open a document without hovering the margin.
2. Move the caret with the keyboard : the + is often missing.
3. If it appears (e.g. after hover), press Tab : focus often goes on and then disapears
4. If focus is on +, Enter or Space : insert menu doesn’t always open.

BlockNote version

No response

Environment

No response

Additional context

1. Show the side menu when the caret / selection is in a block (not only on mousemove), and don’t hide it on Tab / arrow keys.
2. Don’t capture Tab for nesting while the side menu is shown
3. Attach onClick to SideMenu.Button, not only the inner icon.

Contribution

• I'd be interested in contributing a fix for this issue

Sponsor

• I'm a sponsor and would appreciate if you could look into this sooner than later 💖