Since V3.55 terminatorX provides multiple DND-Drop-Targets for use with GNOME / gmc (gmc is the GNU Midnight Commander), Nautilus or the Elightenment File Manager (efm). You can load an audiofile into an existing turntable by dragging it from a gmc (or efm or whatever)-window and drop it over a. the file button (audio-display) or b. (the easier target ;) over the audio-display (the green on black widget that displays the audiodata).
To add a file to the set (== to load the file into a *new* turntable) simply drop the audiofile over the "New Turntable" Button. To load a complete terminatorX-set simply drop the setfile (*.tX) over the "Load Set" button.