Folder portal of different course in unrelated course

Can someone explain why there is a folder portal in my folder “HTML & CSS” to a different folder “Databanken” ? Those two are not related.

This usually means that there is an open portal to the rem that you are zoomed in to (in your screenshot, this is the rem “HTML & CSS”) somewhere within the folder in the In 1 Folder portal (in your screenshot, this is “Inleidende Begrippen”).

Here’s an example from my KB:

I have a folder called Question List + Notes, which has a portal to a couple of rems/documents, one of which is a document named Microscopic Anatomy.

When I zoom into the Microscopic Anatomy document, it says that it is in the folder Question List + Notes (not actually in the folder, but there is a portal that contains this document within the folder).

Hope this helps.