Hi pablo_embasa,
There's a neat little trick to this. You can directly target array-like keys in an object with POST requests to append to them, or directly do a DELETE request on one of the items in the array. Example below:
1, Get current members of an address group named "test_group":
GET /api/v2/cmdb/firewall/addrgrp/test_group
=> addr_1, addr_2, addr_3 (to keep this short, I am showing just the members after the command is run, not the actual JSON output)
2, Append a new address object to it:
POST /api/v2/cmdb/firewall/addrgrp/test_group/member
payload: {"name": "addr_4"}
=> addr_1, addr_2, addr_3, addr_4
3, Remove a single address object from it, but leave the rest:
DELETE /api/v2/cmdb/firewall/addrgrp/test_group/member/addr_2
=> addr_1, addr_3, addr_4