I much prefer using K for check instead of C, which I reserve for "call". List:

K = check
C = call
FC = flat call
SC = smooth call (or suited connectors in different context)
L = limp
PR = pot raise
PB = pot bet
ai = all-in

Example of use:

CPR 99 PF, KRai flop 922 = Call pot raise preflop, check-raise all-in.

I use C for both check and call. It's pretty hard to get it confused, like, "CPR" is never going to be "checked pot raise preflop" likewise "crai" is never going to be "called raised all in".

ch = check, what's the problem?

and cb = continuation bet

In my old notes-style I used to use a capital X to indicate a check and C for call. So a note would look like this:

X-C flop w/ set OOP, vb 2/3 turn/river blanks

Oddly enough I still wrote CRAI. Not hard to see why I abandoned this form of note taking. Now I just write the whole damned thing out since FT gives so much space for notes anyways.

New notes style:

called BTN open w/ 55 (BB), check call w/ set, vb 2/3 turn/river blanks OOP

It's a lot more clear in the "heat" of battle.

I also like to type my flops like this:
567r = 567 rainbow
567(2s) = 567 double suited
567 mono = 567 all one suit

t = two tone = double suited = way easier and m = mono