Hi,
It can be done but not directly from within the GE client - you need
to edit the kml by hand (text editor).
If you do as you have before and create your linestring kml and then
open it in Notepad++ (for example) you can then edit the altitude of
each coordinate of your linestring to reflect what you want - this
could either be alt relative to ground or absolute depending on your
needs. Once saved if you open that file in GE your linestring will now
(if you go to it's properties) show a range of altitudes - "various
altitudes (min=500m, max=1000m)" for example.
As I say you don't get to edit this way in GE but GE will display
handrolled kml that has different altitudes at each coord.
If your linestring is only 2 coords (and the points are relatively
close) then it's simple to set the start and end points at different,
and specific heights, however if your linestring is complicated then,
while still possible, it's more work (and code really) to get a
solution.
(I deal alot with complex paths that need altitude adjustments in
various places where the terrain drops away - for example a bridge
over a gorge - and I need my paths to follow the road including where
the road should follow - over features (like bridges) that are present
in the 3D building layer.)
Regards
Nymor