Can't add files to a subfolder
I have a number of files in my subfolder (all of them articles) and it seems like I can't add any more files to it. I removed a file from it and readded it by dragging, and it worked, but I couldn't add a new file. Is it a bug or is it something I'm doing wrong? I'm pretty experienced with Zotero and never experienced anything like this before.
The most likely reason you wouldn't be able to drag something is the item already exists in the collection.