Hi Huda!
I post my plugins at https://codap.xyz. You will find a number of things there that might be of interest. Some of them eventually get adopted by the CODAP gurus (like Choosy and Testimate). Others, like Arbor, the tree plugin, do not appear in the CODAP Plugins menu or in their GIT repository.
In the case of Arbor, you can find it in my own repository (https://github.com/eepsmedia/plugins/tree/master/arbor), but for right now, beware! I’m having trouble communicating with github, so the very latest changes have not been merged to that repo. If you need the latest code, let me know and I’ll just send it.
Best yet, convince Yannik Fleischer or Sven Hüsing at Paderborn to take over this code…
Schöne Grüße,
Tim