Adding custom buttons
Ok, I have already asked the same in an indirect way, didn't get any answer (that's fine of course) so I will try to... rephrase. You may call it a second roll of the dice!
I want to make a custom button, and then add it in the default (simple) editor toolbar. In Wiki for Smarties and elsewhere one can find some basic instructions on how to use the "edit tool" window for the custom buttons ("add name, add label, add icon"), but not any help about the "syntax" field and how these different types mentioned ("inline, block etc. etc) work.
I would appreciate any hint, even a link where I can study and understand how to correctly fill these fields.
Let me add that the specific button I want to add is the "external page link" button, that disappeared after the latest upgrade to 12.0. The one that brings the pop up window where we choose some text and add the url link.