Workflow Group selection: Doesnt show all Groups

Hello,
i am currently working on a Project.
I figured out permission concept for the Users that will use that cloud.

On my evaluation i noticed that in Workflow settings you can only choose between 20 different Groups.
That is a huge Problem, i cant set restrictions for every group and the whole Projet is currently on hold.

I hope someone can help me.

Sorry for the bad English.