SPELL=<Spell letter>Where Spell letter is Q, W, E, R, AA, D, F, 1, 2, 3, 4, 5, 6, T (trinket)
Shows to GoS what spell do you want to use.
Important.
TARGET=<target>ENEMYHERO, ALLYHERO, SELF, ENEMYMINION, JUNGLEMINION, NOTALLYMINION, ALLYMINION, GOSTARGET and so on...
Shows to GoS target. If took GOSTARGET, will use targetselector/selected minion from GoS.
Important.
TARGETSELECTOR=<id>Shows how GoS must seek for target.
For example, id 1 - is "lowest health", id 2 is "lowest AD" and so on.
Minions have almost the same.
RANGE=<range>Where Range is any number.
Not important, if not specified, will take standart range from hero library.
Can ceil range, if you don't want it to be max range
BLOCKEDNOTBLOCKEDNot important, if not specified, will take information from hero library.
Can specify, if minions can block spell or they can not.
PHYSICALMAGICALTRUENot important, if not specified, will take info from hero lib.
Can specify type of spell damage.
LASTHIT=<offset>Not important. This word will change logic of spell - it will cast spell only if it will kill enemy.
If Offset is exists (like LASTHIT=10 instead of LASTHIT), then it will cast spell earlier (like, if spell do 100 damage, then it will be casted on minion with 110 hp. 110 - 10 (offset) = 100 (spell damage)
MELEEFORMRANGEDFORMNot important. If this word presists, GoS will execute only lines that is matches.
And much more... my head is kinda want to explode now, but there at least 100 KEYWORDS that can be used.
How we must use it? Easy!
I said that there is 6-7 textboxes? So, we selecting first textbox in "combo" menu and writing:
SPELL=Q TARGET=ENEMYHERO TARGETSELECTOR=1
Now, every time we press SPACE, GoS will seek for appropriate target for Q from all enemy heroes, using targetselector 1 (lowest health). If found - will cast Q on this hero!
If Q is on cooldown (or there is no enemies nearby), script will orbwalk to cursor and try to AA enemies as usual.
If we at second line writing:
SPELL=R TARGET=ENEMYHERO LASTHIT (We thinking that we playing Darius)
Now if Q can't be casted, script will look for enemy that can be killed by Darius Ult. If so - casting ulti. And trying to AA next target.
Or, we taking first textbox in LaneClear...
SPELL=Q TARGET=NOTALLYMINION TARGETSELECTOR=10 ("highest HP"), supposing that we playing Evelynn.
Now everytime we pressing V, GoS will do next route:
1) Check, if there NOT ALLY MINIONS nearby, that can be hit by Q? If so, take the one with biggest HP and cast Q.
2) AA any minion.
Now we adding second line
SPELL=E TARGET=NOTALLYMINION TARGETSELECTOR=10 LASTHIT (supposing we STILL playing evelynn xD)
How we also did another fun thing, and route will look like so:
1) Check, if there NOT ALLY MINIONS nearby, that can be hit by Q? If so, take the one with biggest HP and cast Q.
2) Check, if there is NOT ALLY MINIONS nearby, that can be hit by E? If so, are one of them can be KILLED with E? If so, take the one with highest HP and execute E.
3) AA any minion.
But you will notice that this is not really works as it wanted to - it targets closest minion instead of HIGHEST HP. Why? Because by default range of E is 150 (i know this is not a truth, but I must do an example)
So, to tweak this, you simply modifying your string to:
SPELL=E TARGET=NOTALLYMINION TARGETSELECTOR=10 LASTHIT RANGE=400
And how, E will look for target inside 400 range instead of 150.
Those "fast scripts" can be kinda useful

It allows to change used spells on-air, and even control mana%, lasthitting with spells and so much more...