In Tools & Settings > Restricted Mode Settings > Hosting Tools, the Ability to create, remove, and switch among subscriptions option is disabled;
Additional administrators with Restricted Mode enabled still can remove domains;
Installed Plesk versions is 18.0.20 Update #1.
Plesk bug #PPP-45372. It has already been fixed in Plesk Obsidian 18.0.21.
Install the latest Plesk updates.