This works for a 1-to-1 filter, but I cannot find how to use one input (like my parameter) to inform a filter of multiple options.
Right now I have a Parameter informing a single Set-Filter, but depending on which Parameter value is picked, I want a different Set of values shown. I can only get one set of values to display since one Set-Filter overrides the other Set-Filter.
The above reply gets at the heart of what you want to do. Basically, you need to use a parameter combined with multiple filters to achieve what you are looking for.
You would create a parameter, I'll call it YEAR-PARAMETER, with a list of all the years you want the user to be able to select, and that would be the interaction the user sees.
Behind the scenes, you would create a calculated field, something like this:
IF [YEAR]<=[YEAR-PARAMETER] then "Show" else "Hide" END, and then put this as a filter onto the elements that you want to display all years up to the year.
Then you could have another calculated field to do the year plus the previous year, and that filter goes on the other element.
And finally another calculated field that just says if YEAR=YEAR-PARAMETER, then filter goes on those elements.