If you click “New Topic” and drag a video file in the resulting window, the browser redirects to a tab showing the video file and you lose the topic.
Also, the upload button
doesn’t support video uploads, only images
That behavior matches the forum’s current upload handling: the composer accepts images, but a dropped video is treated differently and redirects away from the topic. A practical workaround is to share a short recording through a public media host or convert the key moments to a GIF/screenshots, with a brief description and the browser/JupyterLab versions for reproducibility.