It's actually a lot safer at this point to just say: "I'll fix everything Trump has broken." And that would cover pretty much everything Trump has done. If Biden starts listing things, it can only alienate voters when he hits their sacred cow. There are a lot of Republicans and Republican leaning Independents who are ready to vote for Biden, but maybe not if Biden pans something they like.

Biden can almost just stay home at this point and win. Trump campaigns for him every day and night. Don't "fix it" if it ain't broke.