Media Library Slug

Hi,

I am trying to organise some specific files within my media library to be structured in a consisten format. I will happily do it manually but when I go to edit a media item it will allow you to change some slugs but not others. I cant find any relationship to why it lets you or not.

I would like to filter some specific documents into 2 seperate locations:

https://www.ttthreads.com/wp-content/uploads/VPM/…
https://www.ttthreads.com/wp-content/uploads/VCM/…

I would then like the file name to follow after:

https://www.ttthreads.com/wp-content/uploads/VPM/filename.pdf

If I go to media library it won’t let me edit the items I want but for others it will.

Any ideas?