.pfd File Locking - 'Read Only' Status

There doesnt seem to be any 'locking' of PFD files when they're opened. Currently individuals, or multiple users, can open the same file and overright it. Clearly thats less than ideal!

It also happens with SmartTools, if you export out of SmartTools and open that file in Flow, you can just overright it again while its open in Flow!