Draw power from a portable mobile charger to power circuits
What can I do to make the charger output power on low loads?


You probably can't do anything reasonable. Charging power banks are designed to cut off power when they think the charge is done, when load drops below certain cut-off level. This condition will happen every time you connect-disconnect your project while debugging it.


you can load it with proper resistor, but it will drain the bank battery quickly.
you can reverse engineer your powerbank, determine what kind of PMIC (power management IC) is used, and disable this cut-off function if possible, but it is very doubtful.
You need to design your own PMIC on the top of existing circuit, replace it with power management you need. This new design must have all features to charge and protect the powerbank battery, but will have no cut-off function.