How to make a form field appear when a toggle button is turned on

Vdraper You can also achieve this using SharePoint out of the box capabilities (without using Power Apps forms). Follow below steps:

1. Create Yes/No (boolean) type column in list for showing toggle
2. Format the display of yes/no column using JSON column formatting using JSON samples provided in my answer at: Adding a clickable button to A SharePoint list to update a Yes/No Field - this will turn display of your Yes/No column from default checkbox to toggle
3. Then you can show/hide list form fields using SharePoint conditional formulas. For example, you can use formula like: 

=if([$YesNoColumnInternalName]==true,'true','false')​

Where YesNoColumnInternalName is the internal name of your Yes/No column. You can get the internal name of your columns by following this article: How to find the Internal name of columns in SharePoint Online? 

Follow this Microsoft official documentation for steps showing where to add the conditional formulas: Show or hide columns in a SharePoint list or library form 

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