I know you should always have your coins on a hardware wallet.
But for my trading position I don't want to put the coins on a hardware wallet because that would be too cumbersome but I want to distribute the coins on several exchanges.
In your opinion, what are the most secure exchanges in the world, i.e. where can I be most sure that the exchange will not go bankrupt, be hacked, etc.?
If you have lots of cryptos then yes it would be better to store them in a hardware wallet because number 1 is you can easily afford to get one even the best quality in the market today and number 2 is that hardware wallets are known to be more robust than the commonly used online wallets.
I see that you are also trader and its indeed hassle to just withdraw or depo the coins in an exchange every time you feel the need to trade, not only that but its also time and money consuming (the fees) so why not store a good portion of your coins inside the exchange? Binance and kuckoin are only two of the most safest exchange that I know. I only cant assure that they won't be hacked but maybe they can return your money if ever something bad happens to them.