I was wondering if it’s possible to make a transparent alpha video on the widget. as I have created an AE motion graphic (Animation) and I wanna add it to the widget without the background, I hope you can help me with this 
yea the built in media player / image widget dont handle alpha correctly, thats why you get black background. for widget you need a material that samples the media texture alpha into opacity and a widget that actually draws transparent. i ended up using alpha video player from fab Alpha Video Player - Transparent Video UMG Widget & UI Media Component (UE5) | Fab it has blend modes for straight vs premultiplied alpha + poster/fade, just drop it in UMG and assign your media source. for AE export png or exr sequence with alpha, or prores 4444 if you need a single file - mp4 h264 cant carry alpha btw