Ah yes, doing it as separate scraps is a lot less messy. Though in the
end you then probably have to keep using multiple scraps, even if the
idea was to warp it into a nice shape so you can draw it up as a single
scrap.

Anyway you may use all morphed sketches in one final scrap (Torsten). Take care if you add another xvi file it will go above of recent one. So the way is to switch visibility of mesh (xvi itself) to off and move morphed sketch (xvi - IMGn) to correct position: select that sketch in "Background images" field, check coordinates of cursor (lover right corner of map editor window) where you want to place it, write those coordinates to fields next of “Move to” and press Enter. Manually move sketch to exact position. There is the bug in Therion that th2 file will remember only 3 such positions. For fourth and next you should repeat that last step after you open th2 file again.

To move to your sketch is the shortest way to click on point or line in “Object section” - on the top of sections menu.

I tested out the "sketch-warp" option (that goes directly in the
.thconfig file, not inside the layout). "plaquette" gave a very good
resulting shape for my demo case (and was really fast!), but made the
lines jagged and hard to see. "linear" preserved the sketch best but
caused more distortion. "point" took forever, but the result was
absolutely excellent. It is interesting to me that the default "line"
gave the worst result of all options.

The Therion book does not mention "linear" or "point", and could do with
an update. I found more details on this very old tutorial:
http://marcocorvi.altervista.org/caving/tbe/m_04/m_045.htm