I would like to play around with the movie option, but I cannot find a way to open or import a movie.
You can attach a video file by either right click on a flow card in setup mode and select Video / Attach from the context menu or drag and drop the video file into the time line in play mode.
Which formats are supported? .avi, .mkv and .mp4 format aren’t recognized.
Dorico supports the same formats as Cubase and Nuendo, described here: https://helpcenter.steinberg.de/hc/en-us/articles/115000808250-Video-support-in-Cubase-and-Nuendo which includes avi and mp4 containers, however there are a huge number of different video formats inside the container, and only a subset of those are supported (though the list is getting longer all the time)
Note that we discovered a bug yesterday where videos won’t attach if they have a long path (this is already fixed for the next update). So ensure the file has a short name or isn’t in a deep directory structure.