Forgetful Workspace Workaround
Years, years I tell you, of InDesign forgetting my Workspace over various versions and preference and Workspace resets and complete uninstalls and reinstalls.
Since Adobe doesn't care, I sicced ChatGPT on it, I gave it the name of my custom Workspace (which you should be using anyway), and it created a file called "SetDefaultWorkspace.jsx" that you drop into the folder inside the ID application folder: Scripts > Startup scripts. I had it create the code and create the file so i could simply download it.
When I set the Workspace to something else and then quit the app and rebooted it, my workspace was selected as the default; every time.
This ends those annoying popups Adobe won't give us control over. The only way to avoid them is to create a Workspace, use a startup script as outlined above, so that ID doesn't think you're a newbie.
The propt would be something like:
Create an Indesign startup script called SetDefaultWorkspace.jsx that I can download, and tell me where to place it. My Workspace is called [your Workspace name].
