Exclude files without trees

Hello.

is it possible to exclude a specific file type without a defined tree?
For example we want to backup a whole server but want to exclude some files.

In the "backup object summery" is only / listed. When we define our excludes there it dont work.
I guess thats because we have to define the exlucdes for the specific directorys.
But that would be unpleasant. 

So is it possible to do it without define trees or recursiv for the root directory /?

Thanks in advance!