I tried it and successfully used "restore" by using spaces instead of comma,
plus you need to specify the path or name (will be created in the same dir of electrum) of the to-be-created wallet file:
Examples:
restore "KziuQS1uPq2i4XRg7gxGacWoTBMgTUVrU2Bm2c1e17GdMTAWMguq Kzs8YzmX2HXzKE8dxpm1y6vyb3g5abTio1f7SroKNoecZg1cHL3a" -w "C:\****\****\delete_later-nc50lc1"
restore "KziuQS1uPq2i4XRg7gxGacWoTBMgTUVrU2Bm2c1e17GdMTAWMguq Kzs8YzmX2HXzKE8dxpm1y6vyb3g5abTio1f7SroKNoecZg1cHL3a" -w "delete_later-nc50lc2"
If you want to change the address type, add the address type before the private keys just like in the GUI:
Example:
restore "p2wpkh:KziuQS1uPq2i4XRg7gxGacWoTBMgTUVrU2Bm2c1e17GdMTAWMguq p2wpkh-p2sh:Kzs8YzmX2HXzKE8dxpm1y6vyb3g5abTio1f7SroKNoecZg1cHL3a" -w "delete_later-nc50lc3"
Make sure that the daemon is running.