Docker Compose Gluetun YAML Splitting Lines

[kinsham 1]

In this fragment of my Docker Compose YAML file for Gluetun, I have a long line for the 'FIREWALL_VPN_INPUT_PORTS=' line which goes off the terminal screen. I'd like to split this line into multiple lines for readability.

I've not had any success trying the various YAML line splitting recipes found online, so could anyone suggest whether/how I could do this?

Of the various recipes I tried, the YAMLLINT YAML syntax checker doesn't throw any errors but the docker parser/checker does and Gluetun fails to start.

It works fine all on one line.

Thanks
 ---
   services:
       gluetun:
           container_name: airvpn
           image: qmcgaw/gluetun
           cap_add:
               - NET_ADMIN
           environment:
               - VPN_SERVICE_PROVIDER="airvpn"
               - SERVER_COUNTRIES="United Kingdom"
               - FIREWALL_VPN_INPUT_PORTS=6081,41181,4055,4056,28424,28425,6080,4080,4081,27243,27247,10720,2669,8112,....
               - TZ="Europe/London"
               - UPDATER_PERIOD=24h
           devices:
               - /dev/net/tun:/dev/net/tun
           ports:
               - 3843:4080        # http (4080)
    ....