Add select simple with the above options and the same storage as it is in User Usegroup field to the registration form.

Hmm, isn't it very dangerous?

The user could change the id values (10 or 11) to 7 and get Administrator rights.

I did the following select simple field. It seems to work.

I have the Groups "Freelancer (10)" and "Ausschreiber (11)" and "Test (12)"

When i use tamperdata to manipulate the field when registering to 12, the user becomes the standard Group "Registered" instead of "Test (12)".

Is this a safe way? So nobody can register as "Administrator" or other Group?

Thanks a lot for your help!

I just retested this and I can assure you - if you use select simple user will only be able to select values that are available - in case of usergroups this means if data is tampered with (changed manually), default usergroup will be used as defined in the User Manager Options.

That is perfect. Thank you Klas!