RE: Design option lost in Sandbox BC
Hi, I tested it and also encountered this problem. Super users can design, but for normal users (with D365 EXTENSION MGT) cannot.
Super:

Normal User:

When I add Super permission to the user, Design can be seen.

Finally I found the reason, D365 EXTENSION MGT has been deprecated. We have to use new permission set, EXTEN. MGT. - ADMIN. But in D365 EXTENSION MGT group, Microsoft hasn't updated to the new one, causing this problem.


Also, as far as I know, this has nothing to do with Disable personalization, because that just limits the ability to Personalize.
Hope this will help.
Thanks.
ZHU