As the title points, the fact that the player STILL can't set the formation for your party in BG3 is more than a bit puzzling to me.
We are SIX patches and a year into its release, the thing was pointed as an issue already during the three years of Early Access, not to mention that for how poorly it was implemented even DOS 2 had it already (buried in the ESC menu where a lot of people apparently missed it, but still...).
I doubt it would be something "challenging" to code into the game and while it's arguably just a minor annoyance in the base game with 4 characters (where there only so many versions of a square or a romboid you can form with your party members) it becomes absolutely obnoxious once you start modding the game to add more characters (something that Larian explicitly said it would endorse, given that they didn't want to consider making a larger party the default) and all the extra ones start shaping up what's arguably the stupidest, most impractical default formation the genre has ever seen.