I want to edit my save file. How do I do it?

[fierce bear]

just do the main story and challenge (side) missions

idk why people think the game is grindy when they're just playing it wrong
playing custom matches is not the way to go
there's so many side missions in the story and challenges on each difficulty that you can easily get to level 30 by doing them

[craggy ibex]

I mean they can ask others to transfer own-made save files.

[lavish matrix]

Part of the reason I'm asking is also so I can mess around with ridiculously overpowered weaponry and watch the game implode as a kind of stress test.