Create a new animation rawr file in Open Other > Animation (Glaxnimate). Close Glaxnimate then put the rawr file in Timeline. Go to the rawr file’s Properties Tab and click Edit to go to Glaxnimate. In Glaxnimate go to Document > Timing to extend the duration of the clip. Save the rawr file then close Glaxnimate. In Shotcut, go to the rawr file’s Properties Tab and click Reload to update the duration. When you then go to the rawr clip on the timeline to extend the clip it will not actually get longer but the dialog that comes up showing the duration of the clip will keep running for as long as you keep pulling on the clip. Demo.