I've not used "Target Finds" and "Target Sorts" so I don't know how they work (just try out changing something and see how it works, I always do this).
Judging by name "AIThinkInfestor" is "Tactical AI Function" - a function from standard triggers library. Trigger functions is used for some units that has many castable abilities or require more difficult logic than simple autocast. You can write your own tactical AI function and set that field to the "script identifier" of that function (function real name in compiled galaxy script). Example AI Think Function (from "Mutators COOP" lib, "Heroes From The Storm" mutator):
CT_AmonHeroTychus_AIThink Options: Action Return Type: (None) Parameters ------- All AI Think Triggers Must Have the following three parameters, no more no less Owner = 0 <Integer> AIUnit = No Unit <Unit> NearByUnits = (Empty unit group) <Unit Group> Grammar Text: CT_AmonHeroTychus_AIThink(Owner,AIUnit,NearByUnits) Hint Text: (None) Custom Script Code Local Variables Target = No Point <Point> AbilityRange = 0.0 <Real> AbilityDamage = 0 <Integer> AbilityAoE = 0.0 <Real> ------- Comment Score = 0 <Integer> ------- Comment OrderVariable = No Order <Order> Actions General -If (Conditions) then do (Actions) else do (Actions) If Or Conditions (Number of Living units in NearByUnits) <= 0 ((((Mutator Amon Tychus Toss Grenade, 0))) is valid for AIUnit) == False (Cooldown of cooldown Abil/MutatorAmonTychusTossGrenade on ability Mutator Amon Tychus Toss Grenade on unit AIUnit) > 0.0 (AIUnit order list has an order with ability Mutator Amon Tychus Toss Grenade) == True Then General -Skip remaining actions Else ------- Comment Variable -Set AbilityRange = (Value of Abilities MutatorAmonTychusTossGrenade Range for player Owner as an integer) Variable -Set AbilityDamage = (Value of Effects MutatorAmonTychusTossGrenadeDamage Amount for player Owner as an integer) Variable -Set AbilityAoE = (Real((Value of Effects MutatorAmonTychusTossGrenadeDamage AreaArray.Radius for player Any Player))) Variable -Set Score = 1 ------- Score is tallied per unit potentially hit, 1 point for Vitality >= Damage, otherwise (Vitality/Damage) points Variable -Set Target = (Returns the best location to place and AOE attack on the group with the specified parameters ((Units in NearByUnits having alliance Enemy with Owner, with at most Any Amount), 3, AbilityDamage, Score, AbilityAoE, (Position of AIUnit), AbilityRange, c_unitAttributeNone)) ------- Comment General -If (Conditions) then do (Actions) else do (Actions) If Target != No Point Then AI -Suggests order ( Toss Shredder Grenade (Tychus) targeting Target) to AIUnit using tactical AI logic General -Skip remaining actions Else