Congrats on making your first post here in the Community. I'd be more than happy to assist you with running a report of outstanding checks.
I recommend running the Check Detail report that's available in QuickBooks Online. From there, you can customize the report to your liking. Here's how:
Go to the Report tab on the left-hand menu bar.
In the "Standard" portion of the reports page, scroll down until you see the Expenses and vendors section.