Pyros
<Silver Donator>
No it does convert all the resists, in separate lines. You can easily find examples if you search the trade site for very high resist items. Ingame I believe they're displayed as separate lines but on trade they're combined, but you can see that's 3 suffixes into one roll.Yeah, mostly because the wording is so weird for the case where you have an item with fire and cold res but you want lightning. Obviously you can't take an item with 40 fire and 40 cold and get 80 lightning, but that's what the text would imply to someone who doesn't know much about how gear works. I have no idea what it actually does though. Pick one, convert it, delete the other would be my guess, just because that's how an asshole would design it.
But yeah, I really need my item to stay exactly the same but just remove the word cold and replace it with lightning. I've learned long ago to never assume anything in POE works how you would want it to as a player, however.
That means you can make godly chaos resist items by using the chaos alloy, by converting like 100+% worth of ele resist into one fat chaos roll and fix all your chaos resist at once. Obviously you still need to fix your ele resists but it's a lot easier that way.
Only takes 2ex to test though if you're worried, grab a random rare with 2 resists and buy a flux of the other elem and use it to check.