Custom Magic Items - Tracked Abilities

[Ambush]

I'm working on a custom magic item in my campaign that has a special ability. 1/day the weapon can cast the spell Tree Stride. As a workaround, I've added a tracked resource with one charge and added the spell to the custom item. However, if the item ends up with more than one power, this will fail. For example, the Instrument of the Bards (Canaith mandolin) allows each of the following spells 1/day (Fly, invisibility, levitate, protection from evil and good,Cure wounds (3rd level), dispel magic, protection from energy).

Currently, I can't find any items that implement something like this independently, but I believe it can be done. In the editor, under the General/Ability tabs there is an option to create an "Item Power Helper" which seems like it might do it. When I bootstrap one onto my weapon I get the errors below when I add it to my character. Clearly I'm missing something. Am I barking up the wrong tree with this ability? Is there some other way to get there? Is there an item that I've missed that would give me a template to do this?

I get the errors:
Attempt to access non-existent parent pick for a top-level container from script Location: 'eval' script for Component 'Ability' (Eval Script '#1') near line 5
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Attempt to access non-existent parent pick for a top-level container from script Location: 'eval' script for Component 'SetName' (Eval Script 'Append livename Details') near line 30