Change SPO List Details Pane to Custom View Form

H-M-P Unfortunately, this is not possible using the SharePoint default capabilities. Power apps customized forms open only when using new/display/edit forms and not while using details pane.

However, you can prevent editing list items via the Details pane (or via Quick Edit/Grid view) from List settings > Advanced Settings. When the PowerApps form is used to govern field settings with logic rules, it often makes sense to prevent edits via the details pane. 

You can also vote on below idea on Power platform ideas forum which is relevant to this topic: Override SharePoint lists details pane with customized Power App form 

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