The smallest example that proves how to build your own toolbar with superdoc/ui. Single file, no framework.
A custom toolbar binds buttons to commands. The same surface holds built-ins (bold, italic, underline, ...) and your own (example.insertClause). Each button subscribes per-id via ui.commands.<id>.observe(...), so changes to one command don't re-render the rest of the row. Click handlers run ui.commands.get(id).execute().
ui.commands.register({ id, execute, getState }) puts a custom command on the same surface as built-ins. The example registers one and binds a button to it the same way it binds the bold button.
This example shows that flow and nothing else. No threading, no resolve / reopen, no comments, no mode toggle. For the full Custom UI sidebar pattern, see demos/custom-ui.
pnpm install
pnpm devClick the buttons. Bold, Italic, Underline toggle on the current selection. Insert clause inserts a fixed snippet at the cursor.