You can use a Group of Dimensions which shows only the one you want to show in the chart/pivot table, but use it later in reports, or you can add a if statement to say when and how you want to show that dimension, if that's what you want.
Just to be clear, I think an IF statement to conditionally show a dimension is only available in Version 9.
I don't know of a way in version 8.x to conditionally show a dimension on a pivot table or even to have it functioning but not showing, it can be done very simply on a straight table in the presentation tab.
One option might be: Change the text colour to white and make the column size very small but you'd need to check what the impact of this is on the report as I don't ever use reports in QlikView.
You are right. We all should indicate the version of QV we are working with, as I never used version 8.x so I don't know how many changes and which changes are from one version to another. And sorry for the inconvenience. For what is worth, I'm using QV v9.00 SR1