The "::filter" convention is filters. We also have parameters (for some time now, although only in v0.11 added UI for them). With parameters you can do:

SELECT country_code AS "cc::filter", COUNT(1) as num_users FROM mytable WHERE lifetime_spend > {{minimum_lifetime_spend}} GROUP BY country_code

And minimum_lifetime_spend will render as an input box. Currently we only support input boxes (of different types - number/string/date), but there is a plan to add support for dropdowns there as well.

Allowing self serving without knowing SQL is the goal, but I believe it will take time to do it right. We focus on delivering a great product for people who know SQL, and allow them to give more interactive result sets to other users using things like parameters.

So not sure if our goal is less ambitious, but we just take a different path. And that's good I guess, it would've been not interesting if everyone built the same thing, the same way :-)