Hello there, david-hall.
Yes, you have a way to show inactive projects in QuickBooks Online. Once a project is inactive, it's considered as deleted.
To show deleted projects, here's what you'll need to do:
From there, all deleted browsers will show up.
To learn more about Projects, you can consider checking this article:
I'm here for you if you have further questions, just leave a comment below. Have a great day!
That's correct - the QBO companies have this option, but you will not be able to restore a deleted project in QBOA files. I would suggest using the 'blocked' status (if something is preventing you from continuing) or 'cancelled' if you would like to retain a record of the project.
I would encourage you to use the feedback option in-product to submit this for consideration in later updates.