I have a plugin I'm trying to adapt for TinyMCE 5.x, and I can't figure out any way to dynamically change the toolbar button icon after it is already created. I can create/define multiple icons in the registry using editor.ui.registry.addIcon, but the 4.x commands for changing the image/icon seem to be gone.
Does anyone have any idea where in the TinyMCE 5.x API I can find a function to change a toolbar button icon?
(Researching this question on Stack Overflow only yields a question from 2017 directed at the TinyMCE 4.x API.)