Can't export an animation with a transparent background in Toon Boom Harmony Advanced

I’ve been trying for the past 2 days to export an animation with a transparent background, but I can’t. I’ve looked up ways to do it, most of which say to export with PNG4 (which doesn’t appear at all), and nothing works. I want to edit a moving background into the animation but I can’t because the background of the animation always has a black background. I have no other pictures interfering or colour cards.
I’m kinda stuck.

You will need to use a video editor to assemble the image sequence into a movie.

In Advanced or Essentials go to File => Export => Images => there will be Colour Mode and File Type drop down menus. Choose Colour with Transparency and then the file type. If the file type does not support transparency it will not show Colour with Transparency as an option in the drop down menu.

It would have been better if you could simply choose Colour with Transparency and then only have the file types which support it show as options. But they all show up whether it is Colour or Colour with Transparency so you have to do it manually one by one.

Of those that are listed, these are the file types that retained the Colour with Transparency option: OPT, PNG, PSB, PSD, SGI and TGA

Essentials and Advanced: https://docs.toonboom.com/help/harmony-14/advanced/export/export-image-sequence.html?Highlight=export%20images

The Colour Depth bit/channel field is only big enough to show one digit. I think it is 16 when it shows a 1.

“If you want to export images with transparency, you need to select the file type that supports this option, such as .tga, .psd or .png. Harmony supports 16 bits per channel RGB and RGBA .png files. The Colour Mode menu changes according to the File Type selected. For example, selecting .tif will result in only having “Colour” as a Colour Mode option, whereas .png will have “Colour” and “Colour with Transparency”.”