Safely parking E-scooters in Okinawa

I found a place that rents foldable e-scooters in Naha that would work well for my group if we can park them safely. Almost all the places we will be going have free parking lots for cars attached to the Facility. Looking at the facilities via Google maps satellite view and street view, the parking lots are usually over half empty. Some of the places we are going to are far outside of Naha city.

Is it acceptable to park a group of scooters in a free car parking lot?

Is one bike lock cable strung through multiple scooters enough protection? I've seen some articles about increases in bike theft. I don't see any bike stands that we could thread the scooter cable through for extra protection.

Have you asked the rental shop?

I asked about how to lock them up about a week ago via email. No response so far.