How can I bulk-change the folder permissions on macOS?
chmod has an -R option to apply changes recursively to a whole directory tree but I strongly recommend to not use it for your scenario as you can break quite a lot of things by applying it in places where you shouldn't.

Instead


Log into your Mac as an administrative user and rerun JDisk. Not sure it will solve all your issues though as the tool seems to be cross-plattform and may not be aware of access right handling on macOS
Check out the answers in How can I figure out what&#39;s slowly eating my HD space? for other tools