5. iOS Shortcut
Since this project revolves around being used by an iOS Shortcut, I've included it in the repo files so you can import it to your iOS device. The shortcut can be run alone or in the Share Sheet when selecting one or more videos. Note that the Share Sheet will not show the shortcut if you select any photos.
You can download the iOS Shortcut that integrates with this project in the repo files here. Open it on your iOS device to import it to your Shortcuts.
You'll need to configure a few parameters at the beginning of the Shortcut.
Click on the 3 dots of the imported Shortcut.
Scroll down a little bit and edit the following fields in your shortcut
Note: some fields may differ from the screenshot if this documentation was not updated.
Once the shortcut is installed and configured, you should now see the new "Merge Videos" action in your share sheet. Just select some videos from your Photos app and press the share button. In the screenshot below, my action is at the top, because I added it to my favorites. However, when you first run the action, it'll be at the bottom of the share sheet.
