Well, you have those experience clumps, 8x compressed and such, and using it gives 3k + levels.
But nothing to store the already turned into player experience level.
I'd suggest something a handheld or even a block to store it in like EnderIO's Experience Obelisk or Cyclics Experience Pylon.

Currently on Oceanblock modpack, the only form of exp storage is using Mob Grind Utils drains with your Unstable Drums as the liquid storage, but it's not fast enough (on a server).
Recipe: 4x Un or Semi stable ingot, 2x 2xCompressed Experience, Unstable Drum.

I already know of those, unstable drums are = to supreme, but what I'm asking is something that can just grab all of the experience and store it a block much akin to the Experience Obelisk/Pylon, as 3.6k levels goes to waste on death.
The singularity tank/drain only holds 32 buckets, Unstable Drum/Supreme Black Hole Tank holds the 2billion mlb of liquid. and even if I was on single player, the 4 drains (standing on each block corner) only drains 5 ish buckets a second, but with 3.6k levels (4200 Ender Dragons killed), it'd take almost a week of just standing on the blocks doing nothing.
Hence why I'm asking for an instant source of exp storage. ;P

Not an answer, but I'm also playing Oceanblock and you can use Singularity tank from mob grinding utils to save your exp, or probably you can use a supreme black hole tank? (from IF) Not sure the problematics that appears when playing in servers.