FOR CLUB TEAMS:
If all you want is to save player A to the wing, and change around the defensemen after a new signing, what you should do is unlock the 10,000 PES credit Transfer mode, then go into Free Transfers, select the team..
The first 11 in the list is the starting line-up, from there you can select your player and shuffle the squad members around.
it's usually:
1. Goalie
2. Left centre back
3. right centre back
4. Left wing back
5. Right wing back
6. Left winger midfield
7. Centre midfiled left
8. Centre midfield right
9. Right winger midfield
10. Left striker
11. Right Striker
So using that, you can shuffle you player names and move people from the bench or reserves into their positions in the first team. Then, when you end the editing, it'll autoload every time you fire up the game!
For National Teams/Classic teams:
This time you have to do what Zygalski suggest above and save formations to the slots on your memory card and load them each time.