Thanks, I hope it will be of use for not only me.
GoogleEarth is a nice free instrument for simulation of flight plans in 3D, especially in more challanging terrain, when taking care not to violate LineOfSight to the takeoff location (where radio control and vrx equipment is usually located).
The drawback here is, or at least I don't know how, to set different endpoint heights along the path in GoogleEarth while creating the path. This is overcomed by saving the path in .kml file, and then editing it in a text ediotr like Notepad++.
<LineString>
<altitudeMode>absolute</altitudeMode>
<coordinates>
27.73969535063608,42.29710351265771,110 27.75700061676305,42.28759759045708,190
</coordinates>
</LineString>
After adjusting heights, save and reload the .kml file in Google Earth to have the desired 3D path. Simulate and further edit. Moving existing path points preserves their new preset heights.