You might find it easier to work with a normal gallery to play your videos instead of a Wix Pro Gallery as the Wix Pro Gallery is a Wix app and if you try to interject it with code, it may try to override or ignore the used code.
Or you can look at trying the Wix VideoPlayer instead.
https://support.wix.com/en/the-wix-editor/video
Along with a single video player.
https://support.wix.com/en/article/adding-and-setting-up-the-single-video-player
One way you could possibly do it is to add a setTimeout function to a coded button to start playing a video.
Then you can have a hidden button shown after a set amount of milliseconds which will then give the user an option to skip whatever is currently playing and move on to play whatever you have this button setup to play instead.
See here for VideoPlayer API.
https://www.wix.com/corvid/reference/$w.VideoPlayer.html