For a git repository, it's possible to checkout branches into separate folders. In your case, d:\myprojects\myclient\mysolution is the main working tree with master checked out. You can checkout bench into another working tree,
git worktree add <path_to_bench_worktree> bench
path_to_bench_worktree could be any valid path, for example d:\myprojects\myclient\mysolution_bench.
The 2 working trees share the same git folder, d:\myprojects\myclient\mysolution\.git. You can modify files and commit changes in both working trees, one for master and the other for bench. You can create more working trees when necessary.
When you think a working tree is not needed any more, you can remove it,
# in the main working tree
git worktree remove <path_to_bench_worktree>
You can also remove path_to_bench_worktree first and then in the main working tree,
git worktree prune