TMP won't display inspector window

I am having some major headaches with TMP after attempting to download the latest version from the Asset Store. Prior to this things were working fine and I had TMP elements within various screen overlay UI canvases. After the update all hell broke loose.

All my existing TextUGUI components lost reference to the relevant script and refused to work. I decided to remove TMP altogether from the project and do a clean import. Import seemed to finish without errors but now when I try to create a new TMP-Text gameobject from the right click menu in the hierarchy, the inspector for the component only says "Multi-object editing not supported". In the console I'm getting the message:
"Instance of TMP_UiEditorPanel couldn't be created. The script class needs to derive from ScriptableObject and be placed in the Assets/Editor folder."

I deleted the TMP asset folder and reimported numerous times. Keep getting the same error.
Any idea what's going on?

 

Alright it seems I ran into the same issue as in this thread: https://forum.unity.com/threads/upg...0-56-0b2-seems-to-have-broken-project.509215/

After following the elaborate close scene/delete tmp/ close unity/ open unity / reimport procedure, it seems to be working again. I have to say, though, this was not a good user experience.

 

Once the DLL's from a previous version are loaded which would happen if you have an open scene, the upgrade process does get more elaborate since we can't unload those DLLs.

The migration to the new Unity package manager (UPM) version of TextMesh Pro also has its own complexities but once on that new UPM version, the upgrade process will get much easier and almost transparent.