Not sure where the wallet files are exactly located in MAC, but I would imagine it should work if you just change the file's name from default_wallet to whatever you want. There is no need to add or edit any extension.
EDIT:
You should find a wallet folder here which contains the wallet files. If you're scared you might corrupt the file (although I don't see how), just make sure your seedphrase is safe, or take a backup of your wallet first.
EDIT:
Quote
On Mac:
Open Finder
Go to folder (shift+cmd+G) and type ~/.electrum
Open Finder
Go to folder (shift+cmd+G) and type ~/.electrum
You should find a wallet folder here which contains the wallet files. If you're scared you might corrupt the file (although I don't see how), just make sure your seedphrase is safe, or take a backup of your wallet first.
I followed what you quoted and it worked. The wallet name is now changed. Thanks for the help!
