POST https://YOUR-NETWORK-DOMAIN/rest-api/custom-parameters/{parameterId}/delete.do
Removes a parameter from the registry. Targeting rules that read it keep working, but a list parameter's rules go back to comparing the whole request value. A built-in parameter cannot be deleted. Requires the CUSTOM_PARAMETERS admin permission (Admin → Targeting presets → Custom parameters).
using var client = new HttpClient();
var request = new HttpRequestMessage(new HttpMethod("POST"), "https://YOUR-NETWORK-DOMAIN/rest-api/custom-parameters/genre/delete.do");
request.Headers.Add("X-Api-Key", "YOUR_API_KEY");
var response = await client.SendAsync(request);
Console.WriteLine(await response.Content.ReadAsStringAsync());