Ask HN: What Feature to Add Next

I have this side project https://pidtuner.com and I am struggling to decide what to add next.

I could improve the underlying algorithms to be faster and more robust (handle better some edge cases) which would improve the success cases for users. This change would not bring an economic cost (apart from the time spent), the downside is the users wouldn't inmediatly notice the upgrade.

I could also implement saving a project on to the cloud, so users can recover and share their results. This would probably help the discoverability of the project, but would be costly for me since I would have to pay monthly for a server to store the user data, and although a thousand people use it a month, nobody donates a dime.

I am passionate about this project and want to improve it but cannot decide how.