There's been a few times now where I'm dealing with songs of abnormal pattern lengths where I want to get an easy idea of how long sections are without having to constantly do subtraction in my head, so being able to select certain patterns to estimate it's song length (the same way you're able to do with selecting patterns to export only certain sections of a song) would be a really nice addition to the program. If you don't want to clutter the UI with an extra button in the Player drop down, you could just add a second line under "Approximate song length:" that says "Approximate selection length:", and it'd also be nice to select rows and be able to do it for that, but given that it's not currently possible to export certain rows I'd understand if it doesn't make sense to add.