Bed heating stops when paused by filament runout sensor
There is no easy way to keep the bed heated during pause
Looking at the sourcecode, I am pretty sure that the current version (10/29/2019) keeps the heated bed at the right temperature.
Features are built into the firmware. You need an Arduino and some wires to write new firmware to the built-in SOC. Adjusting the code should be as simple as commenting a single line.
That is some serious shortcoming of the CR-10 S5! I can't imagine a reason why not to leave the heated bed on.
The command that keeps the heated bed at temperature is in Marlin_main.cpp:5664:
Source code link