Checked out a few clients; none were satisfactory. Satellite.earth is nice (supports hierarchical view), but doesn't seem to have notifications (ugh).
Discussion
what OS? I like Amethyst on Android. on Linux, Gossip is my go-to: https://github.com/mikedilger/gossip/releases/tag/v0.10.0
macOS
I was wrong; satellite.earth does support notifications (it is on top-right corner).