Create subgroup for project with similar name

I have a project which is hosted under a group and I just realized that this project grew quite large so it would fit a subgroup (also because there are multiple aspects to this project). Now I want to use a subgroup that has a similar name as the project has right now and then splitting the project further within this subgroup.
Suppose the project is hosted at Group/Project and I want to split it into two parts called Foo and Bar. They should be hosted under Group/Project/Foo (and <...>/Bar respectively) where Project is now a subgroup of Group.
When I try to create a subgroup of said name it fails because that name is already taken by the project. What would be the correct way to proceed? Do I have to move the project to some temporary placeholder name, then create the subgroup, then move the project to that subgroup and then rename it?