The museum creator in current build has very many bugs that we fixed - they could cause very many issues

Same here:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3453395506

Adding tools up to three on the screen.
The paint brush was stuck for many minutes, until I went berserk changing all the menu's and options I could around the workshop.

P.S Note: Steam makes your screenshots private as default. That is the reason for 404 bad requests or appearing blank. Change them to public and the links work.