get request: https://url/to/cockpit/api/collections/get/test?token=xxtokenxx&filter[link.display]=test
https://url/to/cockpit/api/collections/get/test?token=xxtokenxx&filter[link.display]=test
post request: {"filter":{"link.display":"test"}}
{"filter":{"link.display":"test"}}
Avoid whitespaces and linebreaks in json bodies.
This should work. If not, have a look at