Oh Four! Ah, that's on me then.
And also yes and no. Four has mentioned before in LU that he doesn't work on magic swords since they are nothing but unwarranted surprises, and earlier on when Wild offers to lend Twilight the Sheikah Slate Twi turns him down since he's 'not a fan of magic'.
So, I think Four would find some of the tech cool, and might be a bit curious about whatever the hell Robbie is doing that results in glowing swords, I don't think he'd be so interested that he'd want to get involved.
Would he sit and watch Robbie make a sword out of Sheikah Tech? Probably (and mentally criticize him since I can't imagine Robbie would adhere to any sort of safety protocols at all). Would he try his hand at making one of those glowing swords himself? Absolutely not. He is very happy just hanging out with the Blacksmith Guild and teaching them some of his tricks and helping arm the Hyrulean army with regular, normal, not magic swords.
Mostly I imagine Four spends his time after being rescued from the Yige leading up to the Calamity hiding out in a forge and hanging out with the other blacksmiths. And taking advantage of his small size to avoid Robbie because he does not work on magic swords and Robbie can't seem to understand that anything that glows falls into the 'magic' category. He'd probably spend more time watching the researchers if Robbie stopped trying to make him help build glowing weapons.
