An example preset is attached (DO NOT FORGET SAVE YOUR CURRENT PRESET!)
There is "Save/Recall" Action which has "focused" option. So "Recall focused" choose the strip in focus, track or bus. Then you just want set explicitly which parameter you want control, f.e. Volume. For that in the "Stip" Action select "<No>" as the strip type and "Volume" as parameter. That effectively keeps current choice (so focused strip), but set parameter to control ("Volume", but can be "Pan" or followed by FX/Send Action, etc.). The third Action is Value, you probably want "Endless" option (may be "Accelerated") for the knob, I guess that you know already.
PS. "Recall focused" with self defined "StripType" Software Set ("Track"/"Bus" as states) in "save strip type to" option and "Set engine state" set, put into Monitor Timer Ultra with priority 0, is the way to monitor current focused strip type. Than it can be used in "Strip" Action (as "strip type") or other places which should be focused strip type sensitive. Such complexity make sense in case you do some monitoring (f.e. for build-in display). The method in the example is simpler to understand since it doesn't use monitors nor software sets.