I played around yesterday with multiple selections in album list and tried to see if double click with multiple items works the same way like in Facets. If you make a multiple selection and double click the last (not selected) node the result is that the last node will be deselected with the second click of the doubleclick and not included in the playlist interaction. But if you then repeat the doubleclick the selection of the last node will be kept.

Maybe i found the reason for that strange behavior. It happened for my suprise to see a cursor in the selecton of album list nodes (i don't know why it isn't showed always and also don't know how to make it visible). Holding down ctrl-key and clicking a node selects that node but the cursor doesn't follow the last selection (like in Facets). Just a doubleclick that selects and unselect a node moves the cursor so that the next doubleclick keeps the selection.

On the other side continuing a multiple selection with a middle click works fine. Exactly that doesn't work in Facet as there a middle click doesn't cause a selection so that just the middle clicked entry is included in the playlist interaction but not the selected items.