Hi Andy
I'm sorry for the inconvenience this may cause, but currently, the KW37 Family of MCUs does not support the BLE Mesh Specification.
About the JN5189, K32W, and KW41Z, these devices support Wireless Mesh communications protocols, such as ZigBee and Thread, but they don't support BLE Mesh either.
Currently, some of the devices in the new line of Wi-Fi® + Bluetooth MCUs do support BLE Mesh specifications. Could you please take a look at these?
Please let me know if you need any more information.