Mendix Modeler has a subversion and its functionality is very limited; cannot revert, etc.
A fully functional subversion within Modeler is handy and useful.
A document at https://docs.mendix.com/addons/APM/installation-steps says that 'Install a subversion.' That's ridiculous because Modeler already has internal subversion. An entire design is not well-done, I think.
Thanks for the comments. But, I knew it and a separate tool is not very valuable for this case.
See the documentation here: https://docs.mendix.com/refguide/version-control-scenarios
Only note that the Tortoise version you have to install is 1.7 and not 1.6. With this tool you can revert etc.