Almost all of the informant symbols are supported, but you have to use the NAG format for them (a dollar sign and then a number corresponding to the symbol).
Here's a list of all of the symbols that are included:
$1 !
$2 ?
$3 !!
$4 ??
$5 !?
$6 ?!
$7 □ (only move)
$10 =
$13 ∞ (unclear)
$14 +/= (white slightly better)
$15 =/+ (black slightly better)
$16 +/- (white moderately better)
$17 -/+ (black moderately better)
$18 +- (white is winning)
$19 -+ (black is winning)
$22 white is in zugzwang
$23 black is in zugzwang
$32 white has a development advantage
$33 black has a development advantage
$36 → (white has the initiative)
$37 → (black has the initiative)
$40 ↑ (white has an attack)
$41 ↑ (black has an attack)
$132 ⇆ (white has counterplay)
$133 ⇆ (black has counterplay)
$140 ∆ (with the idea)
$146 N (novelty)
I included symbols for all of the ones that are supported by my browser (chrome). Hopefully someday the missing ones get added too...
The most common symbols are definitely the first handful, but the last four are also commonly used.