As the title states, it seems the F (focus/frame) key is no longer working in the static mesh editor in 4.10 Preview 4.
I’m pretty sure it was fine in previous previews and definitely worked in 4.9.2
It does however work fine in the main editor view port.
I have been able to verify that the F key does not focus on the mesh in the static mesh editor. This is currently a known issue, UE-21140. Thank you for your report.