There may be other options, but for me - this requires a script. This rackspace uses the VST3 of Deelay (free version).
Deelay.rackspace (74.4 KB)
The script was fairly simple: scaling the slider value to a range of 0 to 3 (which selects one of the 4 widgets). Note that I have also set these widgets to be in a radio button group, so you can click on them directly as well.
The script is one directional only - so it will select the mode button based on the slider, but the slider won’t move if you select one of the mode buttons.
Var
MODE1,MODE2,MODE3,MODE4 : Widget
MODESLIDER : Widget
MODES : Widget Array = [MODE1,MODE2,MODE3,MODE4]
On WidgetValueChanged(newValue : double) from MODESLIDER
Var modeIndex : Integer = ScaleRange(newValue, 0, Size(MODES)-1)
SetWidgetValue(MODES[modeIndex], 1.0)
End