Assistance with New Button in Sidebar

[Urimidos]

Greetings everyone,
I'm having trouble adding a new button to the Sidebar.
After working myself through Jeff's Tutorial (https://www.fantasygrounds.com/forums/showthread.php?25234-Jeff-s-Excruciatingly-Simple-Extension-Tutorial), I can't add a Button via DesktopManager.registerDockShortcut2, it keeps throwing a LUA error on startup within the extension.

It's a quite simplistic Extension (yet) and I am quite despaired that even the first hurdle seems to be so unmountable to me.

Could someone please take the time, check the attached extension and enlighten me?

EDIT: Typo from hell :p

EDIT: Nevermind, got it... comments are not always your friends :rolleyes:

[damned]

welcome Urimidos

Have a look here - https://www.youtube.com/watch?v=c9RyzgeiQOI&list=PLsgd1zJLdiKW23yt4X2qc_9w1TWQfTPUA&index=10
You are missing some windowclass info

[Urimidos]

An answer from the famous damned himself, thank you very much. You're a real legend, MoreCore truly is a piece of art, mate.

I'll take a look at the video as soon as possible and hopefully it will dispel some of my other struggles...
e.g. why the he** I can't find the definition for the windowclass "mc_locationslist" (NOT "mclocationslist") which is used in registerDockShortcut2.
Right now, I guess all these list windows (Items Locations, Organisations,...) are built dynamically somewhere I can't find yet.