Hello @MKuyk,
I agree with @ToanDN, for scheduling and filtering you need only a project parameter.
for tagging, you need a shared parameter.
In your case, there something else going on.
I believe you added a parameter to the Revit Category: Conduit, Conduit Fitting and Conduit Run.
Unfortunately, You can't create colored filters in Revit for the Revit Category "Conduit Runs" and you can't select the "Conduit Runs" Category in a Revit View.
Conduit run schedules only show the Conduit runs that are made with the Revit System family 'Conduit Whiteout Fittings'. It does not show the runs that are made with the conduits with fittings.
When you fill in the parameter in your conduits and Conduit fittings Revit will not show that parameter in your Conduit schedule.
That is why you see the empty value of your parameter in the schedule.

I added the Project parameter to the Revit Category 'Conduit and Conduit Fittings', selected the run, and gave them the run number.
Then created two filters for Conduit and Conduit Fittings as you can see below.

In the schedule, you see that I can give the runs different numbers than the Conduit and Conduit Fittings in the View.

I hope you understand now how this works in Revit.
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Kind regards,
Robert Klempau
Senior Consultant AEC
Cadac Group AEC BV