I read somehwere that ledger nano only lets you have 4 different coins in there at one time, surely that is not true?
Actually that is NOT true. You can load 4 different apps (or less) at one time in the Ledger (to manage them) but you can hold all of the supported coins there. Remember that the coins are NOT physically inside the Ledger, it is only a device that holds your private keys for you and lets you sign transactions. Your coins are in the blockchain.