Macros modifying all initiative values

I'm looking for a way to modify the initiative values of everything in the initiative tracker with a single macro, including the initiative values of custom items not linked to a token. Is there a way to do that?

Without the API (a Pro subscriber perk), I think your limited to only the characters you add manually to the macro. So you could have a macro that, say, added 6 specific characters to the turn tracker, but every time the composition of the group changed, you'd have to change the macro. I don't think there're any way to add cusrom items not linked to pokens through macros though. That's something you really need the API for.