The list of values populate based on the values in the sheet's underlying table.
It's a hack but consider this. Create a second calc, and for the values you don't want them to see, set the second calc value to "ZZZ" or something that will sort to the bottom. Use that as a filter, and display it. (I would disable the "ALL" option.) On your dashboard, mask over the ZZZ part of the filter so the user cannot see it. That would give them access to the A, B, C choices, without being able to click the ZZZ, so the ZZZ rows would always remain in the selected values.
The reason I would disable the ALL option is because if they have all selected and uncheck ALL, then all values get de-selected, and then they would only be able to include A B and C and ZZZ would remain deselected.
Thanks for your response. What do you mean by "mask over the ZZZ part of the filter..."? I'm very new to Tableau and haven't encountered that before.
See attached. (V10.1 superstore)
I made "Central" to be permanent like you need in your workbook. I covered it with a container (that I shaded yellow so you can see it.) If it were white, the user wouldn't see it, and also wouldn't see "ZZZ".
Filter hack.twbx 391.5 KB