JAL-1677 allowed splitFrames to be saved/restored to the project, but currently, when a splitFrame is restored, its desktop X,Y appears to be based on the default 'new window' position (just below and to the right of the last newly displayed alignment window). Ideally, the splitFrame X,Y position should be saved and faithfully restored (with scaling/relocation according to desktop geometry changes) like any other first-class window in the Jalview desktop.