Stacking multiple fields in a split row

This question was asked in another post, but a confirmed solution wasn’t presented before the topic closed. I am hoping to to be able to stack multiple form fields in slot #4 of a 4-field row that only appears based on conditional logic selections from field 3 on that same row.

So, for example, let’s say field 3 asks “What warehouse do you use?” with a dropdown menu of 65 warehouses across the country. The user chooses St. Louis and then field 4, which was empty, now reveals one of 3 travel dates: Jan 1 - 7; Jan 7 - 14; Jan 14 - 28.

And bonus points if you know how to show those fields pre-filled with placeholder text and LOCKED for editing, since these dates aren’t changeable.