bug or not?

when your cursor is in query field or any other editable field.
Then, when you select two times [plus - minus] expansion node in database tree( in the left) the name of database or name of some table inside will appear in the query editor

This plus+minus click is considered as doubleclick I guess. Probably a bug in VirtualTree which should not fire the OnDblClick event, but ho hum...

okay, then. it makes sense now.