If you're still on the (now dead) Fast Ring for Windows 10 Mobile, Microsoft recently pushed out an update bringing some of the Photos app's editing capabilities to Windows 10 Mobile users.
It doesn't bring in any of Windows 10 PC's more interesting features such as video editing, but it does allow you to ink on top of photos, select filters, and more. The version brings it to 18011.13438.0. The Photos app on the Fast Ring has also become rather slow for some, particularly on devices that aren't officially "supported" by Windows 10 Mobile.
It's possible that this update was made in error, considering Microsoft is no longer focused on bringing new features to Windows 10 Mobile, and the Fast Ring for W10M has come to an end. Microsoft may roll back these changes if so, but if you're a W10M die-hard, you'll at least get to enjoy these changes for the time being.
Thanks to Vjay and Hacer N for the tips.