I understand your needs and we sometimes struggle the same way. I think it might have to do with the steps being right behind you as a person comes in to the cabin of a Seneca. I have installed a handle on the screen door, thay are adjustable to fit any screen door and you can get them at Camping World and other camp supply places, and that helps some, but it will also come loose and sometimes has to be tried a couple of times. Not certain about your Seneca, but our latch has a vertical grab on the forward edge and once you get it almost closed, you can grab that and pull until you hear that sound of it latching. I guess a "Loop" style handle or drawer handle could be attached there to allow a better grip. But it might get in the way of closing the screen.
My wife just says, "Don't slam it, that doesn't work".
Ric and Jan Golding
2016 Jayco Seneca 37FS