Using Arduino IDE 1.6.12 Hourly Build 2016年09月21日 04:14 with Windows 7 64 bit

When you have 3 or more tabs(including the main sketch tab), adding or renaming a tab does not cause the tabs to be arranged alphabetically. This is a problem because after the main sketch file the tabs are concatenated alphabetically and it's logical that the program flow will follow the tab order. If the sketch is closed and reopened the tabs are then arranged alphabetically.
clipboard01

This issue doesn't occur with Arduino IDE 1.6.11