Change user Role on Collaborative Space

I am trying to change the role of a user for a Collaborative Space on the 2018x Cloud, however I can't find how to do it. The user is already a 'Contributor' in the Collaborative Spae and I would like to change his role to 'Author'. On the '3DSpace' App, I can 'Add Member', but I can't change the assigned role...

Anyone knows how to do that? Thanks!