MCreator can get stuck at loading screen at Loading workspace data ...
This bug was reported by some users at this ticket: https://mcreator.net/tracker/issue/44216, but this ticket is about a different issue.
Current fix (1.8.0):
If this happens, the best option to recover the workspace is to go to user/workspace folder and change the extension of backup-* files to .mcr. Then copy these backups to a safe place, reinstall MCreator and import the workspace .mcr backups in the freshly installed MCreator.