Totally open to discussion about this... let me start... So the idea about the XP is that it's the score that you are _likely_ to get if you play the song (based on your settings per instrument/difficulty). Once the song is played, though, having it match up isn't really that useful, IMO; you increment the play count, and move on to the next song. Is there a use case where you _need_ to match up the score you just got with the one it predicted? (If you want to see potential scores, then you have the score charts to look at -- although, admittedly this takes more effort to get to.) Perhaps the better solution (which I will probably get to at some point) is to set XP calculation per song, per instrument (rather than per difficulty level, per instrument).

What I most often use it for is when I finish a song, occasionally the game just won't tell me the XP (or if I'm in multiplayer it gives me the XP of some previous song) and I like to use rbdb to look up the XP that I gained from that song before I move on to the next one. On V2, if I for example expected FC but got GS instead, I just clicked the dropdown and changed it. The process to do the same on V3 just takes a lot longer, so a tooltip with a chart would be a nice shortcut. [Full background: I use an Excel spreadsheet that I made to enter each XP score that keeps a running total of my average, and proximity to other teams in the leaderboard, so that's why I want the XP from each song as I play it, and the game doesn't always give me what I want, especially in multiplayer]

The new Rivals Gadget should be what you're looking for! :D