When creating groups for access of documents, boards etc. It would be easier to administrate the access control if it was possible to add a group in a group.
Then you create a group with the supplier name containing all the supplier project members. Then you create a access group and add the supplier group in it.
When a new member is added to the supplier group all accesses will come automatically and you do not have to add the person in every group needed to get the correct access.