Nice job, Marcelo,
That’s a good workaround. I had seen some discussions of filtering output, but since most people here are not at that skill level, I didn’t recommend it. You’re at a higher level. 🙂
That could be reverse engineered, too. I’ve looked at output of that columns plugin (and others), and then used just a bit of HTML with those same classes in the CF7 form, and voila, instant columns, no filtering. 😉 What’s also interesting is that GeneratePress comes with a grid CSS file automatically, so the same can be done without any plugin if one takes note of those classes, grid-10, grid-30, grid-50, etc.
Dave