I can't edit new world names, I always have to leave them as "New world". This is on 0.7.6 and 0.8.0 alpha 2. It may just be my tablet, I havent seen the problem on any other devices.
Nexus 6 2013
MCPE-6032
New world name
Resolved
Cannot Reproduce
0
(Unassigned)
Unconfirmed
Tablet - Android - Asus Nexus 7
0.7.6, 0.8.0 beta build 2
Retrieved
Cleaning up old issues, please reply if affecting 0.9.3