We can mass-select pieces within a bounding box by clicking and dragging. We can add / remove single pieces from the selection by ctrl+click.
Suggestion: Add a way to deselect pieces with a bounding box, if it doesn't already exist. I tried Ctrl+clickdrag (adds to existing selection, but doesn't remove from it), Ctrl+Shift+clickdrag and Ctrl+Alt+clickdrag.
Use case: A line of thin terrain pieces need to be selected. These overlap a considerable number of other pieces, so would need a click-drag to select the thin pieces, then some means to unselect the other pieces. Alternative is selecting (or deselecting) each individual piece by hand.
Removing pieces from the selection is done with the middle mouse button. This applies to clicking on a piece as well as area-selections.
Yes, this is probably not the most intuitive "key" for this function, but well...
Awesome. :) Thanks for that.