There isn't a feature right now to narrow down to show just topics you have marked as Helpful. There is an option to narrow down to show just the topics you have either Followed or responded with Me Too (Liked). You can also narrow down to find questions you have posted or have responded to. You can do that by clicking on your name in the upper right hand corner and selecting Profile. This opens up a list of the Conversations you are currently following. There is a little dropdown at the top of the list where you can change to Topics you have Authored, Followed, and Me Too'd. The option to find Helpful hasn't been integrated yet, though I did pass this feedback along to our forum providers as a feature that my users and I would like to see as hopefully there are a number of questions that could be added to a User's Helpful log.