iControl REST API - Update/PATCH Signature-set

How can I modify/update an custom signature-set to remove/add specific signatures via REST? Some articles point to possible use of $filter in the URI but I cannot seem to get it right. PATCH to the set via full list of signature reference works but I would like to know if it would be possible to NOT have to supply the entire list. Essentially, not do a rip/replace on the set. Thank you very much in advance!

I am targeting the custom signature-set - /mgmt/tm/asm/signature-sets/[signature_set_hash] but cannot manipulate the "signatureReferences" object for add/remove on specific signatures

Also are AS3 extensions available for ASM? Getting a 400 when trying the add function.

https://clouddocs.f5.com/products/extensions/f5-appsvcs-extension/3/refguide/as3-api.htmlpatch-operation-objects

[{"op": "add", "path": "/signatureReferences/", "value": "link": "; }]

{ "code": 400, "message": "Could not parse/validate the Signature Set 'XXX'. Unknown field 'op'", "originalRequestBody": "{\r\n\"op\": \"add\",\r\n\"signatureReferences\":[{\"link\":\"\"}]\r\n",

"kind": ":resterrorresponse"

}