The algorithm of bitcoin is set to be limited so when all bitcoin has been mined, the miners will no longer be able to receive block rewards because there are no more coins to be generated. But why this?
Because unlike fiat that keeps being printed and causes inevitable inflation, the bitcoin supply is capped and is avoiding inflation. So the production of "new coins" ie. the block reward has to be reduced until it reaches zero where the entire supply has entered circulation.
This happens about a
100 years from now!
If it’s easy to spin up another Bitcoin, then there no limit
You can copy bitcoin's code, you can also copy bitcoin's blockchain but you will never create another bitcoin, you will create an altcoin which would be considered a shitcoin that nobody uses.
So to answer your question, you can't create more "bitcoin".