How to get rid off custom cropping presets in Lightroom ?

Hello all,

when i create a custom crop preset in LR4 it comes at the bottom of the list with the possible crops.
This is becoming a bit of a mess with all the crops that i don't need anymore.
I want to clean up the list but can't seem to find out how.
Anybody knows the answer?

And while we're at it, anybody knows how to give them names and not just the ratio numbers?

Thanks for reading, ciao, Han