With some tweaking, you can increase this number in some degree. E.g. with 1st IF you divide conditions to 2 condition groups, and use 6 nested IF's for both of them. Something like
This doesn't mean it will look pretty, or easy to follow up. Or that such formula will work with reasonable speed for big tables. But anyway, in such way you can instead 7 nested IF's use 2*6=12 IF's, or 4*5=20 IF's, or 8*4=32 IF's, or 16*3=48 IF's, or 32*2 = 64 IF's. The last number is theoretical maximum