In the Cambridge lexicon we find:
ὁσοσ-οῦν ὁσηοῦν ὁσονοῦν , Ion. ὅσος ( η ον ) ὦν indef.relatv.adj.
I can’t tell what case, gender and number όσὦν would be in the Ionic dialect. They’re breaking from their usual pattern since for adjectives if the adjective has a special genitive ending they write gen. before the ending, but for adjectives they normally list η ον as the fem and neuter endings but they don’t put them in parentheses. It looks like the genitive plural to me but I don’t know they would write that down since that would be obvious. They did something similar here:
ὁποσοσ-οῦν ὁποσηοῦνfa ὁποσονοῦνna also Ion. ὁκόσος ( η ον ) ὦν
In Attic, ὁσοσοῦν is the relative adjective ὅσος, “how much/many” with the particle οὖν attached, and this combination is generally written as a single word. The ὁσοσ- element of this combination declines just like ὅσος itself, and the -οῦν element remains the same in all genders, numbers, and cases. Thus, ὁσοσοῦν, ὁσηοῦν, ὁσονοῦν, ὁσουοῦν, ὁσησοῦν, ὁσουοῦν, etc. The same holds true for ὁπόσοσοῦν.
In Ionic, the particle ὦν corresponds to Attic οὖν, and in the text of Herodotus the combination of ὅσος and ὦν is generally written separately as two words, ὅσος ὦν, unlike Attic. As in Attic, ὅσος declines normally. There is a further wrinkle for the Ionic equivalent of Attic ὁπόσοσοῦν: the Ionic equivalent of Attic ὁπόσος is ὁκόσος, so the combination in Ionic is ὁκόσος ὦν. (ὦν in the Cambridge Lexicon is the particle, not a genitive ending.)
Of course, whether these combinations are written as one word or two is really a matter of editorial practice. In antiquity, texts were usually written with no spaces between words and without diacritics, and there was only a single character for sigma.
excellent info, thanks for the tip!