How do you obtain your T5008 slips to combine them if you have more than 500 and TurboTax can't download from CRA for automatically? Must each slip by combined manually?

Because you have over 30 T5008- You will add the amounts from each box and enter them as one T5008 slip in TurboTax. For example, enter the sum of all box 20s from all your slips in box 20 in TurboTax, and the sum of all box 21s from your slips in box 21 in TurboTax, etc.