Shadows in a 3d model should not be tied to geolocation and date/time. Sketchup can represent pretty much anything and MANY contexts are not buildings or traditional objects and therefore should not be tied to real-world sun locations.
As @RTCool suggested, a simple checkbox to allow for either geolocated sun angles OR user setting would be more appropriate.
Good suggestion. There are a few workarounds at present. One is the extension Solar North https://extensions.sketchup.com/en/content/solar-north which allows you to rotate the north direction to any angle you wish regardless of geo-location. The second option is using a rendering plugin in which case you can turn off SketchUp’s default sun and use HDRI or artificial light sources as desired.