Our User Manual currently doesn't cover the feature "Edit->Record Movie". It's missing in the menu description:

https://docs.kde.org/stable/en/kdeedu/marble/commands.html#idp7444112

and we lack a dedicated chapter that thoroughly describes:

- Requirements (detailed but still generic/distribution-independent description on how avconv/ffmpeg needs to be installed)

- Step-by-step description for creating a movie (description of the settings dialog, further steps required etc.)

The new Chapter could be added right after "7. Download Map Regions". So it would become the new Chapter 8 and 9. Command Reference would appear right after it.

If you run into stuff that doesn't work please file a bug report on bugs.kde.org