It's important to note that Toonly is not a video editing tool. If you intend to add another video to your project, we suggest that you export your Toonly video first and use a third-party video editor to merge your videos.
Toonly: Can I upload Video Animations?
Learn that Toonly is not a video editing tool and does not support uploading video animations. To merge videos, export your Toonly project first and use a third-party video editor.