That’s not really anything to do with the Meraki MX, that’s the Windows client dropping the connection. Generally, after the VPN is established, the Meraki MX knows nothing about what is happening with the client it just sees a stream of traffic to decrypt/encrypt.
I’d have a look at some of the Windows forums. A quick Google reveals you may be able to achieve this by adding the KeepRasConnections value (REG_DWORD value, set to 1) into the registry as a parameter to the RasMan service [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\R asMan\Parameters], but I don’t if this really works, works for Windows 10, or works in the switch users scenario. What this claims to do is stop a VPN connection being dropped when a user logs off.
Good luck!