Is it possible to send BTC from a specific address? How to do it?
You can send bitcoin from any address you have in your wallet, except in case if amount of coins is smaller than minimum transaction fees.
I would suggest having a good address management and labeling properly, that would make it easier to use coin control option for sending coins.
Or maybe there is another way to transfer internally from address to address or from addresses to address or from address to addresses?
You can send coins to yourself, but you also have to pay transaction fees for this.
There is no way to move coins without that in self-custodial wallets.