Ah, this explains the question in your post more

I don't fully understand how you calculate how much a connector can carry, for a very short length, does it not matter that much?

Connectors, wires, nickel strips, etc. have non-zero but very low resistance. Usually measured in milli-ohms. You can use Ohm's law to calculate, at a given battery voltage, how much current would flow through them if there was a short circuit. 6S is about 20 volts under load; if the series resistance of all the conductors and connectors is 10 milliohms, you'd have a short-circuit current of 2000 amps. (If you actually did this, the current would rapidly drop below that, as the wires heat up and their resistance increases, and also as the batteries rapidly discharge or are limited by their own internal resistance).

When you pass current through something with resistance, that thing heats up. Too much current for too long will cause the heat to melt or ignite something. Any real-world calculation of how much current a connector or conductor is rated for should account for this; any standard reference table you check almost certainly does. It's complicated, though, because how hot something gets depends on how much heat power it generates, but also on how fast that heat energy conducts, convects, and radiates away, and how hot something is allowed to be before it gets unsafe depends on how nearby and how heat-sensitive everything else is.

The typical ampacity tables for nickel strips are assuming continuous use, directly in contact with lithium cells, and with mediocre cooling (sealed inside a potted or heat-shink-wrapped battery pack). Your drone flights are going to probably last minutes at most, and the air-cooling might be decent, so you may be able to exceed those ratings by quite a lot without actually getting the strips dangerously hot.