I've been trying in the config, is this really possible or is it not possible?

Curiously, the Sweet Berries mostly give me the same quality as the ones I planted, but with the other crops it doesn't matter what quality I planted them with, it always seems to be as if I planted them with no quality.

I'm leaving my config in case it's something I touched and made that mistake.
quality_food-server.txt

(btw, I asked in the comments, maybe you didn't see it, when I put a tag in effect_list it tells me it's not valid and deletes it)

Thanks for your time.

Understood! Indeed, what I was looking for was that the quality was not lost directly, it seemed strange to me that the diamond dropped in quality to "No Quality".
I see that it was a bug, thanks for the quick fix!

It's handled by comparing the weight of the quality of the crop (if it has reached its max. age)
against the quality to roll (+ making sure the crop / seed multiplier isn't too low)

So if gold has a weight of 2 and iron 1 then:
(2 - 0) / (1 - 0) which results in a 100% chance

For gold it would be
(2 - 1) / (2 - 1) which results in 100% chance as well
But since the default crop multiplier is 0.75 that will turn into a 75% chance
(Default values for iron are 1, so it won't affect anything)

Atm things are a bit bugged, granting a higher quality than intended
But in your case I'm assuming you're talking about planting diamond and at least getting gold
For that you'd have to set the crop and seed multiplier to 1 for gold

Tag config will be fixed, it's missing a validation check for it