If there is something solid under it, rail, board, what have you, put your hat or any object large enough to lift the bellow horizontal. Some bellows are made with a Velcro strap going from the center of the front standard back to Velcro patches on folds further back toward the rear standard. On my RH Philips the strap is 1/2" wide by 3". When the bellow sags you can attach the Velcro strap where needed.
At my age I have found the operator often sags before the bellow.
I saw a guy with a 12x20" camera use a home-made bellows support made from an inverted V of mat board that fit into another piece of board that sat on the rails under the camera. The piece on the rail had strips of mat board glued on at intervals creating slots for the V-piece to fit into. It propped a very long bellows up very nicely.