Including mp4 in slideshow

I am experimenting with videos.  I have read the documentation, but it is a bit short on detail.
I have an existing slideshow consisting of webp images.  I tried adding a video to this slideshow.
I uploaded a test video to my media folder. Then I started with Source>Add a slide on Sldieshowck.
First I tried to insert the link to the video in the normal image link box.  Although I got no error messages, the box remained blank.
So I then left the image link box blank and used the Video button to add the link.
This I was able to do, but the video did not appear in the slideshow.
I then added a random image to the image link, and this sort of worked.  My static image came up on the screen for a second or so and then switched to the video.  Is this the intention?  Should I create a blank graphic to prime the option, or am I missing a trick?  Is there a way I can set the CSS so that the display of the video is the same as for static images?
I'm doing this on my local server, so I can't send you a link.
Can you please advise?

Hi
the slideshow works with images, this is mandatory. The best solution in your case is to take a screenshot of the video homescreen and put it as image for the slide.
You can not have a video, article or whatever if you don't put an image in the slide
CEd