M-Files License Generator MFLCONF file with Groups

I want to create a mflconf file for the M-Files License Generator (using version 1.1.4.0) such that it will generate a license file with a group user limit, as described in https://developer.m-files.com/Frameworks/Vault-Application-Framework/Licensing/#user-limits

It’s not clear to me how to specify in mflconf the required "Array of objects".
I have tried:
 

"Groups" : {
  "type" : "array",
  "helpText" : "Group Aliases:"
},

and

  "Groups" : {
    "type" : "array",
    "helpText" : "Group aliases:",
    "members" : {
      "Group" : {
        "type" : "string",
        "helpText" : "Group alias"
      },
      "Len" : {
        "type" : "number",
        "helpText" : "Max number of group members"
      }
    }
  },

But both alternatives will show as a simple array of strings in the GUI, i.e. no way to specify a Len for the group.

Can someone help with a sample MFLCONF file?