What's the best way to have discounts in Netsuite for multiple GL without creating discount per GL? Example - 25 types of discounts and 15 income account, currently have one discount that goes to a discount gl rather than split the discount based on the income account of the item?

What are those discounts? Are they line level or header level discounts? Have you explored using a custom field, custom segment or standard segment such as Class instead of GL accounts?

Discount for sale and it's at item line level.. we do update the category at line level but as the gl is coded to a specific account, it gets posted against that. Not sure what the alternative can be, In an ideal world it would be 1 discount and based on the item line above the item, it updates against that gl

I agree with the “ideal world” approach. since you have NS you do not need to tie every transaction to a GL account per se, you can use items for that. Essentially have one revenue account, one discount account and separate your revenue at item level.