Hello Darcy_L,
Thanks for bringing this to my attention and for sharing a screenshot of what you're seeing in the mobile app. I'm glad to hear you were able to connect with QuickBooks Online support to learn how feature requests are handled, and I'd be happy to address this part of the equation where you're seeing these suggestions.
From your screenshot, I can see that you're using the Android app for QuickBooks Online. I've just tested it out myself, and I see the same as you do: when you type in a feature request and hit Next, it brings up a list of other similar requests, but when you try to subscribe to one of those, there's an error. The QuickBooks system used to have a process like this, where you could see and subscribe to other ideas, and it looks like the Android app has hung onto some of the coding.
In these instances, I recommend clicking I still want to send a message to ensure that your voice is heard and your feedback is forwarded to the product development team. You can even include a bit about how the app is showing you these feature requests to make doubly sure that they're aware this is still happening.
We love and appreciate all feedback from the members of the QuickBooks family as it helps us continue to grow and provide a product that meets the bookkeeping needs of business owners.
Don't hesitate if you've more questions. :)