I guess I'm being thick. In 8.5 I could highlight a track, hit H (which hid anything not selected)and then hit F which expanded the selected track(s) both vertically and horizontally to fill the track view.  Although the shortcut command in Platinum indicates that "F" re-sizes "All Tracks" vertically to fit project window. It's not doing that at my house. When I hide all tracks except the one I'm working on, pressing "F" does not increase the the track height to fill the window. It remains the same height as if all the  tracks were still visible.

Is the key phrase here "All tracks"?

Apologies if this behavior was changed between 8.5 and X1. I have X1, 2 and 3 but never used them after they were installed.

You want Fit Content which is now Ctrl + F.

Thanks John but I've doing Crtl + F for a week now and that combination doesn't do anything if I have one track showing and the rest hidden.

I just tested and "F" worked unless "Auto Track Zoom" is enabled. SHIFT+Z to toggle "Auto Track Zoom" or use the track view View menu to set the feature.