TinyMCE split button – how to trigger an event on dropdown?

My goal is to style some items on the dropdown menu I get after clicking on the dropdown icon of split button, and to rearrange items via DOM manipulation as a custom function.

My issue is, I don’t see a way to do this. The only ‘on’ events there are are OnSetup (won’t work, the dropdown menu doesn’t exist at that point), and onAction/onActionSetup (they apply only after either applying or choosing an item, which is too late for me)

I’d be grateful for advice on how to deal with this. Hacky solutions are fine too.