well, i extremely dislike the idea of having a combination of the stock battery on top of the external 'raw' lipo connected like that - if that is what i see in there on the picture.
you have real chances here to end up with a lipo fire.
people who use such solution do set parameters to ignore any intelligent battery features and use external battery voltage sensors to control the status of the external power source.
they also remove stock battery completely first and only plug in external ones. or - what i saw - they remove all cells from the stock battery and only keep in there the board with sensors. but, to have both..,.
just plugging it like that, blindly, will not do any good and may fry your stock lipo. you typically only set in parallel absolutely identical lipos, same C rating, same capacity. you absolutely do not want one battery pushing wild current into other battery if they are not identical - a smaller one will most likely explode.
if you really into extended flight time using safe methods - there was one seller on the alibaba who had custom made double capacity intelligent batteries, made by taking actual stock batteries, and 'merging' them to double count of cells.
i really do not know what you will get with such adapter. dji uses high voltage cells of a different chemistry compared to usual lipos one can buy - dji charges to 17.6 something V, a usual 4S lipo charges only up to to 16.8V.
it will not like at all being connected to a 17.6V source. do it all at your own risk.
if you do not know how a 5000mah 4S lipo burns - you may want to check it out online first. it has a lot of lithium in it, it is quite intense.
also, people who do such mods are doing it mostly to set record flight hover times - they disable all other features. such hacks/stunts are not really compatible with a normal usual usage of those drones. you can put 2 5000mah bricks on the
mavic 2 and it will hover with it, but, do not expect it to fly normally like this. it is built in the optimal configuration by the factory. extra weight will be reducing flying characteristics while gaining not much extra time.