Hi i was able to do that:
Custom dropdownlist is created by inheriting from HtmlEditorToolbarDropDownBase
Custom dropdownlist item is created by inhereting from ToolbarListEditItem.
Then i was able to add that dropdownlist to toolbar. But the main thing i dont like is the ditor's low performance and delay, when i repopulate those dropdowns. And i that issue would be solved, i would definetley buy suite that includes aspxhtmleditor.