I am trying to make some automated trade orders for lets say coal and plastic. I set the buyable amount to 99999 so it shall always buy the maximum available. But it says its too much because of its cargo capacity. So I have to calculate the exact available amount before I buy?
So I also can not do something in a loop if not every wares were sold because then the buyable amount is not the exact same?

I want to set a chain loop where my trader take the stuff of lets say coal and plastic and sell it so several systems before it refills.
Its also too difficult to set the loop and each time I enter the ship, I have to set the whole loop again. Why cant I store it?
How do you guys do stuff like this?