What Maarten mentiond and to rename the projectname in the modeler you can rename the mpr file with tortoise SVN:
see https://docs.mendix.com/refguide/version-control-scenarios#file-management-and-java-development for the correct version to download here: https://sourceforge.net/projects/tortoisesvn/files/1.7.15/Application/
cheers 🍻!
You can do it in the Mendix sprintr environment:
1. Go to https://sprintr.home.mendix.com
2. Go to your project
3. Go to Settings > General on the left side
4. Click on 'edit settings', now you can edit your project name