This might be better asked in the general forums since it isn't really a healthcare question. That said, rather than using the raw date for the filter, you can use a calculated field at the quarter level. Something like this:
That can be placed on the filter shelf instead of using the raw date. You can continue to use a relative date filter or you can switch to multi-select list. If you use the relative date, the user will always get a full quarter, but it will start from the following quarter because the date is truncated to the first day of the quarter.
To combat that issue, you can use a more complex calculation to resolve the date to the last date of the quarter:
date(dateadd('day',-1, dateadd('quarter',1, DATETRUNC('quarter',[Date]))))
An example file is attached.
quarter filters.twbx 64.8 KB
Continuing from Jeff's point, I think the only 'true' solution for your request is to change to parameters dropdowns with year/quarter separate and use a calculated field as a filter instead.
Having said that, echoing what I believe you alluded to and what Jeff mentioned, we usually still use calendar dates and truncate it to the measure of time we care about (quarter in this case).
I enjoy using a series of parameters as to default the dashboard to the most recent date in the dashboard and a few set ranges for the users to use. Perhaps this could be useful depending on your use case? Image attached.