In the case of the VMS4 where it's useful to select a specific pane, a [Library],FocusPane control would be needed, with the value being which pane to focus. E.g. 0 for the left-most pane, 1 for the one to the right of that, etc.
If the number of panes can change dynamically, then it would be better to have multiple Focus Controls, e.g. [Library],FocusTrackList and [Library],FocusFeatureList or whatever canonical names each pane will have.
In the case of the VMS4 where it's useful to select a specific pane, a [Library],FocusPane control would be needed, with the value being which pane to focus. E.g. 0 for the left-most pane, 1 for the one to the right of that, etc.
If the number of panes can change dynamically, then it would be better to have multiple Focus Controls, e.g. [Library] ,FocusTrackList and [Library] ,FocusFeatureLi st or whatever canonical names each pane will have.