Hello!
I recently asked this question over in the dev category. I would like to request the feature be added to the plugin api with the ability to add your own custom dropdown menu with items.
The closest I was able to come was to add a new dropdown like so, but it expands the same options as the existing default options cog.
api.onToolbarCreate(toolbar => {
toolbar.addButton({
id: "align_center_button",
group: "extras",
icon: "align-center",
popupMenu: true
});
});
Result: