Go to Tools > User Content Folders to go straight to them.
Go to Tools > User Content Folders to go straight to them.
The wording changed slightly.
Tools > Browse Content Folders
Is there any way to "set" the custom content folder(s), i.e. to customize where the content folder(s) lives?
No. You can keep a separate folder somewhere and import manually from it as needed, but the actual custom content will always be copied to the same resource folders by ArtRage.