I’m sure I’m forgetting something obvious here, but I thought there was a way to apply a rule to multiple two-noun actions like this?
Instead of inserting something into or throwing something at when the second noun is the waterfall:
Inform just gives a confusing error message (“The part after ‘when’ (or ‘while’) was fine, but the earlier words did not make sense as a description of an action. Looking at this as a list of alternative actions: ‘inserting something into’ was okay; ‘throwing something at’ was okay; so I am unable to place this rule into any rulebook.”) which doesn’t indicate which part was wrong.