I'd like to create TASK in bitrix24 with webhook URL. Almost everything is fine (task name, description, responsible, deadline etc...) the only problem is with field with several users (Observers and Participants). I don't know how to add these parameters to the URL :( The documentation is incomplete.
The solution is easy, I didn't see your code but per the API doc, you need to encode the JSON array of fields as parameters into the GET request: this will help you: How should I put json in GET request?
A better approach would be using POST to submit data instead of GET, this way you don't need to do the above, you can send the array as it.
Example of an array of fields: