Hi Mike,
I am sorry for my slow response.
That option "Maximum distance between LD blocks to merge" is used to merge the LD blocks of each independent significant SNPs into a single locus.
But this does not change the LD block of each independent significant SNPs.
Any annotations in FUMA including GWAS catalog is performed for SNPs that are in LD with one of the independent significant SNPs (with > user-defined r2 threshold).
So, to get GWAS catalog annotations in FUMA output, the SNP has to be in LD with one of the independent significant SNPs.
Hope this makes sense.
Best,
Kyoko