Sleep mode.

[LunaMoo]

Nope. It's a very niche feature most people doesn't even know about and among those that do know, most aren't interested in it.

If implemented, it would have an use in like 2 games and people would use it to instantly pass long amount of time for in-game benefits, basically to cheat which is better done by actually using cheats.(There are 3 games known to use it, but third one is for waiting for players to join in multiplayer which is useless in case of PPSSPP.)

If you have an github account, you can go here press the "subscribe" button with the bell on the right side and when it ever will be implemented you'll get an info on email, which might actually be never due to the above combined with tons of more appealing feature requests and issues available to solve.