Thank you for your forum post. Unfortunately, with iOS devices you can’t use Bluetooth to send custom imported maps from one iOS device to another.
On iOS devices, you are able to share custom imported maps using AirDrop. You can share maps and map features using this method. This is the only way to share maps and map features without an internet connection on iOS.
On Android devices, you aren’t able to share the maps, but you can share map features using Bluetooth. You can save custom imported maps to your SD card and then take out your SD card and insert it into a new device and transfer maps like that, as long as the device has an SD card slot.
There is a feature request for this, would you like me to add you to the list?