There are several options that can be considered:
Applying power to CHGIN (plugging in a charger) also wakes up the PMIC
The microcontroller can then set the desired to channel to always be on (EN_SBBx = 0x6)
Some MAX77654 options include a channel that turns on as soon as the battery is connected. These options are listed in the datasheet under the Part Number Decode section
MAX77654 B
SBB1 = 1.8V
MAX77654 M
SBB0 = 1.8V
SBB1 = 1.1V
SBB2 = 3.3V