Selection for table

Hello!

I have a two related columns (string type). It can be represented so:

I need to create a visual with dropdown menu, which will contains values from both columns, but only second column's values are selectable, like so:

That is, I select unique Col2 value and other visuals get filtered. I've made this menu with such table mapping:

"table": {
  "rows": {
    "select": [{"for": {"in": "col1"}},{"for": {"in": "col2"}}]
  }
}

And now I'm stuck in interaction with other visuals because selections can be apply only for categorical view. Is there a way to use selections in my visual or I need to go to other data mapping? I just want to click one unique value and filter other visuals. Thanks.

P.S.: don't offer me to use visual gallery examples.