I disagree with the order here: I think the battery should be disconnected right after step 4. You can do that before touching anything else by gently pulling the pull tab to the right.

If all you want to do is to disconnect and reconnect your battery (because your Steam Deck is not booting up... again...) then with a bit of finesse, luck and a flat plastic tool you can even push it back in without removing the shield. Make sure it went all the way back in.