It is not currently possible to build extensions to the text editor in Jira Cloud. We are in the process of releasing an all-new rich text editor for Jira Cloud. While we expect to support extensibility in the new editor eventually, there is no timeline right now.
Unfortunately, we donβt have an update on this. It is still not possible to build extension for the Cloud Editor, and while this is something we expect to support, there remains no timeline.