This is currently not the easiest thing to implement. However, I can still help you with a workaround.
You would need to create a boolean parameter for each sub-category (e.g. 'Exclude copiers'). Then, create a calculated field called 'Others or members' or something like that, which puts a sub-category in 'Others' if the boolean parameter for that sub-category is True:
([Exclude furnishings] and [Sub-Category] == 'Furnishings')
or ([Exclude envelopes] and [Sub-Category] == 'Envelopes')
or ([Exclude papers] and [Sub-Category] == 'Paper')
or ([Exclude copiers] and [Sub-Category] == 'Copiers')
// ... and so on
else [Sub-Category] end
Each sub-category and the associated parameter that the user can put in 'Others' will extend the IF condition. You now just need to put the pill for 'Others or members' on the marks card for color and show the parameter controls for each boolean parameter.
I am including a v.10 workbook package.
pie chart.twbx 1.2 MB
If the list of subcategories gets very long, it will generate a very long list of parameter controls, won't it?
Yep, that is why I mentioned it won't be easy.
I don't think this is a worthwhile pursuit at all. It seems weird that the user would ever be the sole arbiter of what counts as 'Others' and what doesn't.
Create groups of sub-categories and give the user the ability to toggle between showing subcategories and showing groups of subcategories.
Order the pie slices by Number of Records, and give the user the ability to set the bottom N members to be 'Others'.