Nicely conceived! This is the kind of feature Apple ought to have already delivered with on device models and private cloud compute.

Sending many whole screenshots to an indie mystery box, though, should be a non-starter for anyone without the skills to verify what any given update to this app is doing. Your website's featured use case highlights the risks (to you and users) unintentionally well: "How do I export my passwords?" (I did a double take: was this performance art from The Onion?) If a user opens a plain text file of secrets without closing this app/the help task, what gets captured, sent over the network, and saved to disk? What protections exist for, say, a computer-challenged elderly person's banking details?

A suggestion about the FAQ ...

"Where is my task history stored? Is it private? Your privacy is our top priority. Your task history is stored securely and encrypted on your local machine by default. You have full control over your data."

... This invites unanswered questions about what exactly from the screenshots is stored, for how long, and what design backs the "securely" claim. Being up front about this would invite trust and helpful developer feedback.