More Levels needed in Sheet Menu

We're using your Sheet Menu but need more levels available. For some reason when you reach the 3.rd level in a top menu structure, you can only add 'Sheet' and not 'Group'. I have the following top menu structure configured; [Advanced Filters -> Items -> Dimensions]. When I get to 'Dimension'-level this can only be added as a sheet not a group. I would really like the following structure available [Advanced Filters -> Items -> Dimensions -> Submenu].