[dev] Filtering options in Bulk-Action screen

Hi everyone, I need to filter the options of the combobox "Next ticket state" in the Bulk-Action screen. The options will change depending on the actual state of the ticket and the actual user agent. I read the documentation, but i didn't realize how I can do that. Can someone give me a idea? Regards, Charles K. Schulz P.S.: The version that we're using is 2.1.5