I often need to change network settings

As long as Location in System Preferences’ Network pane is set to Automatic, all network interfaces will be active and macOS will check which can provide an internet connection and use it. If you can’t get online or use network services, choose Edit Locations, click + and give the location a name, click Done. Click the cog under the list and pick Set Service Order to what’s appropriate. In turn, select each interface, click the cog; for any interface you need active, select it and click Advanced, set it up however the administrator has advised – for Wi-Fi, don’t remove networks you need from the Preferred Networks list as that’ll remove them from all locations. Click OK > Apply. To switch between location settings, use the > Location menu.