When I right GURPS stats for monsters or NPCs, I try to compress them down. The standard GURPS PC writeup or short monster writeup is pretty compact, but still takes up more room than is absolutely necessary. I like to write the monster stats in with my room descriptions so I don't have to refer to more than one screen or sheet of paper at a time.
Here is how I compress down the necessary stats for a DF monster into a one or two line set of notes.
For example, here is a (somewhat modified) DFM1 troll, who's gone a little addled from his time in the dungeon:
Crazed Troll (ST 20 DX 14 IQ 9 HT 12 HP 20 Will 10 Per 10 FP 12 Speed 7 Move 7 SM+1 Dodge 11 Parry 11(x2) DR 0 Bite-15 2d cutting C grapple on SM+0 Claws(x2)-15 2d+1 cutting C-2 IT(NB,NV) Regen Dark Vision Berserk(BF)-6 Stealth-18 DFM1 p.31)
In case you can't follow, "Bite 15 2d cutting C grapple on SM+0" is "Bite, skill 15, 2d cutting damage, Reach C, counts as a grapple on SM 0 or smaller opponents." The x2 on claws means it has two, same with the x2 on Parry. Yes, I nested parenthesis. No, that doesn't bother me. I abbreviated some of its advantages into lines I'll recognize immediately.
For me, that's all I need to go on.
It has other advantages, sure, but I've noted the ones I need to remember. If I think it'll matter, I'd add more. It has a bunch of advantages, but I know most of them by heart anyway. I could look up ones that matter if someone throws an obscure spell or something odd happens. I also know my players and the encounter, so if I know sense of smell won't matter or it won't be sneaking up on them or what have you, I'll omit its stealth score.
I could forgo all of those stat names, too, if necessary - 20/13/10/12 20/10/10/12 is pretty clear to me. But I don't want to waste a second parsing them out if I can write them out and save that split second of confusion between "which is Will and which is Perception?"
In any case, that's how I compact down the encounter-critical information I need for a monster so I can insert it into my dungeon's room descriptions. I rarely need to page flip for the actual monster.
Hopefully this "compressed stat line" approach might be useful to other space-conscious GMs.