I asked the second question 8 years ago here and got a “no it cannot be done” reply… 
Is this really the case still? I cannot understand that because it would make it so simple to be able to configure the WiFi while setting up the device and it would just work when arriving on location.
So is it still the case that this reply in the other thread is still true?
OSMC uses connman for the network manager.
You can’t edit configuration files to “pre-configure” a wireless network with connman. The command line tool for configuring connman is
connmanctlbut it does not allow pre-configuration of a network that you don’t yet have available.