When I customise a custom SharePoint modern list new item form with Power Apps and publish it back to SharePoint, I get this block of white space at the bottom of the form. Why is this? Why doesn't the form take up the whole space
This seems by design behavior. I have the same white space, this is how it shows during the opening process of the custom form:
But you can still scroll up and down using the scrolling bar on the right side. So there should be no problem using the custom form.
Maybe you could add your feedback in the PowerApps Ideas forum.
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