I’m sorry to hear that you’re having some problems with playback. In the next update we’ve fixed some bugs in the expression map editor, including the one you’ve discovered where the one that is selected is unpredictable. Also in the next update I’ve added some visual diagnostics in Play Mode that allows you to see which playing technique switches the expression map are active at any point.
There are still a number of limitations of playback and expression maps, in particular for third party VSTs. One current issue is that if you edit the score (especially editing dynamics) then Play Mode won’t update the view until you next play back (usually pressing space twice to start and stop playback is enough to do this) - you shouldn’t need to close and reopen the score.
There isn’t yet much support for playing techniques beyond arco/nat, pizz, staccato and legato, in particular how Dorico resolves multiple playing techniques at the same position. This is all on our list to implement as soon as we are able.