Hi Timo,

You will find we have some system categories things like closed and open job status that will not allow you to delete them at all.

As for the user created ones they are not permanently deleted if they are being used by outstanding Jobs or have been applied to any job at any time in the past.
They are marked as IsDeleted in the database which means for all the jobs that once have or are currently using them it will still show up as a valid code, this is so you don't lose your historical information.
But for new jobs or actions it will no longer be available.

Let us know if you have any further questions on this matter.