Use the Synchronize machine-wide Rider and ReSharper settings checkbox on this page if you worked or continue working with ReSharper and want to share preferences configured and saved in 'This computer' settings layer.
'This computer' layer stores your personal settings, which are not shared via 'Solution team-shared' settings layer. 'Solution team-shared' layer is saved in the solution directory and is read by Rider anyway.
By default, Rider saves its machine-wide settings ('This computer' layer) in the following directory:
When you select this checkbox and restart Rider, the settings in 'This computer' layer are read from and written to the following file:
This is the same settings file where ReSharper reads and writes its machine-wide settings.
If you changed some machine-wide settings in Rider before this checkbox was selected, the changes will be ignored after restart.
To keep these changes, export your machine-wide settings before restart: click Manage Layers in the Settings dialog, then right-click This computer layer and select Export to file. After restart, This computer layer will be pointing to the settings file shared with ReSharper, and you can then import your exported settings there in the same way.