add_wound_treatment_modifier_effect

add_wound_treatment_modifier_effect = {	
	save_temporary_scope_value_as = {
		name = treatment_result_treatment
		value = flag:$TREATMENT$
	}
	save_temporary_scope_value_as = {
		name = treatment_result_outcome
		value = flag:$OUTCOME$
	}


	###SUCCESS###
	if = {
		limit = {
			OR = {
				scope:treatment_result_outcome = flag:success
				scope:treatment_result_outcome = flag:critical_success
			}
		}
		#Infection is always removed
		if = {
			limit = { has_character_modifier = infected_wound_modifier }
			remove_character_modifier = infected_wound_modifier
			save_scope_value_as = {
				name = infection
				value = yes
			}
		}
		#Gangrene is removed if you picked risky
		else_if = {
			limit = {
				has_character_modifier = gangrene_modifier
				scope:treatment_result_treatment = flag:risky
			}
			remove_character_modifier = gangrene_modifier
			save_scope_value_as = {
				name = gangrene
				value = yes
			}
		}


		#Applying correct modifier or removing correct trait (unless there's still an active treatment, could happen if you got treated for a wound and then got infection/gangrene)
		if = {
			limit = { has_recent_wound_treatment_trigger = no }

			#Safe treatment
			if = {
				limit = { scope:treatment_result_treatment = flag:safe }

				#Add modifier or remove wounded_1 trait
					if = {
					limit = { has_character_modifier = gangrene_modifier }
					add_character_modifier = { modifier = safe_wound_treatment_success_high_modifier days = wound_treatment_success_duration }
				}
				else_if = {
					limit = { has_trait = wounded_1 }
					remove_trait = wounded_1
				}
				else_if = {
					limit = {
						OR = {
							has_trait = wounded_2
							has_trait = wounded_3
						}
					}
					add_character_modifier = { modifier = safe_wound_treatment_success_low_modifier days = wound_treatment_success_duration }
				}
			}

			#Risky treatment critical success
			else_if = {
				limit = {
					scope:treatment_result_treatment = flag:risky
					scope:treatment_result_outcome = flag:critical_success
				}
				#Remove a trait level
				if = {
					limit = { has_trait = wounded_1 }
					remove_trait = wounded_1
				}
				else_if = {
					limit = { has_trait = wounded_2 }
					remove_trait = wounded_2 #We do it like this so you can see the trait you've lost
					add_trait = wounded_1
				}
				else_if = {
					limit = { has_trait = wounded_3 }
					remove_trait = wounded_3
					add_trait = wounded_2
				}
			}

			#Risky treatment regular success
			else_if = {
				limit = {
					scope:treatment_result_treatment = flag:risky
					scope:treatment_result_outcome = flag:critical_success
				}
				add_character_modifier = { modifier = risky_wound_treatment_success_modifier days = wound_treatment_success_duration }
			}
		}
	}
	###FAILURE###
	else_if = {
		limit = { scope:treatment_result_outcome = flag:failure }

		#Safe treatment failure
		if = {
			limit = { scope:treatment_result_treatment = flag:safe }
			add_character_modifier = { modifier = safe_wound_treatment_failure_modifier days = wound_treatment_failure_duration }
		}
		if = {
			limit = { scope:treatment_result_treatment = flag:risky }
			add_character_modifier = { modifier = risky_wound_treatment_failure_modifier days = wound_treatment_failure_duration }
		}
	}
}

As written in game/common/scripted_effects/20_health_effects.txt.