That's a pretty good idea to be able to set it directly. It is useful when making maps.
The "Export TopoFusion View Parameters" was added for map creation, too. The files look like this:
TopoFusion viewport parameters
UTMposX=324848.547440
UTMposY=4114284.318567
UTMzone=12
UTMzoom=4.290416
WindowWidth=1942
WindowHeight=1042
TileSet=2285
ArrowInterval=-170
ArrowSize=0.60
ArrowAlpha=178
WaypointIconSize=1.50
If you export one of these you can edit UTMzoom to 4.88 (or whatever). .TFV files can be dragged/dropped into TF to move the viewport and set the zoom.
Let me know if that doesn't work for your needs.