I expect Steinberg suggests that you record it all in Lanes in Cubase in the first place (!)…but there is a quicker way of doing it. It helps if they all start in the same place…
Drag them from the Pool onto a single track.
When Cubase asks if you want them on one Track or different tracks, select One Track.
Then Edit/Move to/ Origin.
Then Right Click the Track and select “Clean Up Lanes”. Should all now be on Lanes on one track.