Ah thanks to lildottie, I have found the write ups of the presentations. One
here where Dr Russell and co asked 12 women with a failed first cycle to increase their protein intake and decrease carbs, and 10/12 (83%) got pregnant afterwards. Impressive success rates but a very very small sample of 12.
Another presentation from the same team here reports a project which got 120 women to complete a three day food diary to record their normal diet before their cycle (not clear if it was their first cycle or not). The group eating higher protein had more eggs make it to blastocyst, and more pregnancies, as did the group eating lower carbohydrate. Of the 36 women who managed both high protein and low carb, 80% got pregnant. Bigger numbers but there doesn't seem to be a full paper. Nothing about whether these high protein low carb women might have been different in other important ways (perhaps they were all younger or did loads of exercise or something)
At the same meeting there was a poster / presentation from Colaci et al here which included 145 women but did not find statistically significant links with protein intake and egg or embryo quality (they did not report pregnancy outcomes)
Generally oral presentations and posters at conferences are not really considered to be super duper high quality evidence (unless they are then later written up as 'proper' papers) but more like interesting findings that may warrant further investigation. I'm not convinced on the basis of these reports that high protein makes enough of a difference, but neither does it look like it does any harm. It would be nice if someone had done a study that recruited a lot of women and asked them to eat more protein, measured this, and compared their outcomes against women who ate their normal diet. That's more relevant to our situation where we want to know what we can do to improve chances.
I might do some more digging around the literature and see what else is out there. I'm keen to have the best chance possible, like we all are, but there are a lot of ideas out there and it's easy to feel bad if you don't do them all - that's why I try to be selective about which ideas to follow!