Hi Propaganda,
The way it works for me is as follows.
1. Select a track and hit GO. This will immediately start playing the track you selected and will re-seed MOTS.
2. If after you have performed step 1, you then immediately select another track and hold GO down for three seconds, this will add the second selected track to the queue immediately after the one that is currently playing and re-seed MOTS (based on the new track)
3. If you repeat 2 above while the original track is still playing, then another song will be added to the queue and MOTS will be re-seeded. In this case the queue will have the three tracks you selected followed by the selection from MOTS.
4. If the three tracks you have selected have been played and you are now listening to tracks selected by MOTS and you select a further track and hold GO for three seconds, this will be added to the queue immediately after the currently playing track and MOTS will re-seed the queue based on you newly selected track. You may have to scroll through the queue to the currently playing track to see this actually happening.
Hope this helps to explain how it works (at least for me).