a) Track/Export Tracks - this works as a mix-down (for audio) or merge (for MIDI) of your complete session arrangement; track solo (S) and mute (M) takes effect on which tracks are mix-down/merged into the export audio/MIDI file; current clip selection doesn't apply here; any inserted audio fx plugins are processed so take track export here as a faster-than-real-time bounce recording.
b) Edit/Clip/Export... - this applies to one clip at a time and thus takes current clip selection into account; only clip properties (gain, pitch-shifting, time-stretching) take effect here; track plugins are not; it's kind of a file copy process only.
the kind that you should be interested in, to emulate clip merge, is the first kind, MIDI track export.
There are two kinds of export in Qtractor:
a) Track/Export Tracks - this works as a mix-down (for audio) or merge (for MIDI) of your complete session arrangement; track solo (S) and mute (M) takes effect on which tracks are mix-down/merged into the export audio/MIDI file; current clip selection doesn't apply here; any inserted audio fx plugins are processed so take track export here as a faster-than-real-time bounce recording.
b) Edit/Clip/Export... - this applies to one clip at a time and thus takes current clip selection into account; only clip properties (gain, pitch-shifting, time-stretching) take effect here; track plugins are not; it's kind of a file copy process only.
the kind that you should be interested in, to emulate clip merge, is the first kind, MIDI track export.
Seeya