There are only two or three RPGs in the history of computers that get this right, Under Rail could be next!
When I click an existing save slot and choose 'Save' that means that yes, I do want to overwrite it. That's why I chose it. Don't make me confirm that I want to overwrite AND click Save again. Process should go like this:
1. choose slot
2. option to change name of save file
3. click Overwrite button to confirm