Ordinarily, this is not possible (yet). Columns are always arrange vertically on cards, and there is only ever one button per column.
However, there is an unsupported way (and therefore not recommended because it can potentially break things at any time). There is a hidden formula Button() that can put multiple buttons side-by-side in a cell or on a card.
Rather than trying to explain how it works, you can just check out this demo.
I learned about this from Filmos here:
But again, it’s not supported by Coda and so don’t expect too much.