Not as part of Dawarich itself, but I think combination of our free tools will do it for you:

1. Convert your KMLs to GPXes: dawarich.app/tools/gpx-to-kml/
2. Merge your GPXes to a single file: dawarich.app/tools/gpx-merger/
3. Import your chonky GPX into Dawarich itself :)

No data sampling is being done as of now, but it might be introduced some time later :)