Thank you for reaching out on the community and telling us about your issue. I believe you're trying to change the category from the sounds of it on the transactions. The easiest way to mass change transactions would be to select the first transaction in the list you're looking to change. Scroll down to the very last transaction and hold Shift on your keyboard then click on the last transaction. This should have everything in-between now highlighted. Next you'll want to hold Control and click anywhere in the blue. From here select edit transactions. You'll want to select category and type in the correct one. Once you've finished you should be able to click ok to have them all changed at once
Please let us know if this helps resolve the issue for you.
Thanks,
Quicken Francisco