Yes, there is.
Searching the forums for "export ter" brings up lots of threads.
Since this is your first post here I uploaded a few files for you to study.
Sort of a welcome-present
This is simply the default terrain fed into a Heightfield Generate (which is then fed into the Heightfield Shader).
The output of the Fractal Warp is the shader the Heightfield Generate uses to create the heightfield.
Use the Heightfield nodes settings and additional Heightfield Operators to shape the resulting heightfield to your liking.
Be aware of the resolution and the number of points used to create the hf. Spikes are simply results of bad/wrong settings (see attached picture).
Once created right click on the green Heightfield Generate node in the network view and choose "Save file as...".
This will let you export the heightfield as *.ter file.
There might be restrictions for exporting files with the Free TG version, perhaps.
Hope that helps. Good luck.
Cheers, Klaus