Go to Inventory, then click on compatible group and then on "New". Enter a name, then select resources. Select all resources and finish. See the list of compatible groups on the next step not having the compatible group listed, as by adding all resources, a mixed group has been created. While on one hand it is good to be a little bit more flexible than before, this also may result in a confused user. We should - add a descriptive blurb on page 1 of the group creation wizard, that explains comp. vs mixed groups - add a section in the docs - re-think if we need the individual entries on the inventory tab for comp/mixed groups, as one may just create compatible +mixed groups on the "all groups" entry.