But you do need a more powerful charger, don't you?
Nope. Your increased pack size will just charge more slowly since it is now just plain bigger. Pumping up the amps on the charger is an extremely bad idea because even though you may have say a combined 14S10P pack, what it really is is a 14S4P and a 14S6P pack wired together, and it is not as robust accepting current as a 10P pack, nor can you flog it like a 10P pack and expect it to slough off the flogging like a true 10P pack could.
Yes. You do it by directly connecting two batteries together - leaving them together - and charging thru one of the charging ports. The second pack will charge as the first one charges... but the current will flow thru to the second battery thru the output port connection, which - unless you have a BMS meant to cover this practice - bypasses a number of charge safety features your battery BMS provides.
This can be done safely, providing you do a slew of things right when you set the whole system up - and this goes pretty deep, involving custom packs constructed with this use case in mind. For that reason it is NOT safe for someone to do if they have to ask whether or not they can do it. The consequences are potentially catastrophic if any of it goes wrong, where 'catastrophic' includes burning down your house and killing yourself and/or your family.
So, while I have permanently parallel'd packs for many years, I don't give how-to's on doing it. BTW if I can at all help it, instead of parallel'ing two packs I have a custom larger pack built that does the job with zero risk vs. just reduced, acceptable risk.
Those battery blenders exist to
mitigate the risk I am describing so unhelpfully above, so you don't have to think so hard about doing something that is inherently very risky. But here's the thing: Sure if done right, they can work (if you read the various feature sets out there, you'll see that not all of them do the same thing). But how do you know the company that made it over in China is expert enough or trustworthy enough to not cut corners? After all, Far Eastern companies who are unaccountable and unregulated as it is are already infamous for playing games. Why would you risk EVERYTHING on the assumption that you're going to find the diamond in the rough?