You can delete any forms you no longer need.
When you open a new tax return in the same account, turbotax auto-creates blank documents for your past tax situations to make it easier to fill them in (like W-2s, charity donation, mortgage interest, and so on). It sounds like Turbtax is creating a blank K-1. If you don't have a blank K-1, you can delete it by clicking "review" or "revisit" on the section, then the screen should show a list of K-1s that you can open, or create a new one. There should also be a delete button next to each K-1 in the list.
