I have a reusable element on a parent page. I want to use a button in the reusable element to show a hidden element on the parent page. Can that be done?
yes,
So you have a Reuseable Elemen with button, that mean there will be N number of button defendign on the number of item in Reuseabel.
and you have a Element on main page you want to show , let say popup. you can add a triger on the button to show that popup. **only thing you need to figure out is, a unique condition, because if Reuseable element have 4 item, there will be 4 button.
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You can also check if parent group item is this item then triger this button condition.