I'm trying to convert from AutoCAD to Solidworks. All our current detail views are rectangle because they're created in a viewport which is rectangle. How can I change Solidworks detail view circle to a rectangle? Is it even possible?
You cannot completely make it a system default, but you can half-way make it a default and finish up with manual detail view style changes.
Tools > Options > System Options tab > Drawings > Un-check "Display new detail circles as circles".
This will make the detail view the profile shape, but you will still have to pick the parent view and change the style to either "with leader", "no leader", or "connected" in order to get the "profile" option.