Since you don't seem to like the idea of just deleting the content from the mods folder, I assume you have files in that folder that you want to keep. If so, I would use Studio to check what files are what. It's more time consuming, but probably the only way.
In the end it's all about deleting each file - Studio does nothing more but allows you to see the image, no matter if it is buy/cas/build. Studio deal with those in the same way.
No matter what you do, remember to delete the localthumbcache file afterwards.