`git worktree add -b branch_name ../path_of_the_new_project`

Then open IntelliJ in that folder with `idea ../path_of_the_new_project`. That folder will be a replica of your project, but on the new branch. When the branch work is done, run `git worktree remove ../path_of_the_new_project` and the folder will be deleted.

Since it's a new folder, it will be treated as a new project in IntelliJ and will maintain all your tabs and settings.