We already have mostly digital currency.

Money is created when a bank creates a loan, by starting with nothing and then splitting that nothing into a credit in one account (the borrower's checking account, usually) and a debit in another (the borrower's loan balance). From there, most transactions are digital where an ACH transfer or similar results in some numbers being subtracted from one account and added to another.

Almost all of this happens on computers, and even before computers it just happened literally on a paper ledger, with paper checks.

You might ask, "wait where does the bank get its money from to be able to allow money to be withdrawn or transferred to another bank?" If the bank doesn't have the liquidity to do so, it can always borrow money from other banks or the government, with the last resort in the United States being the federal reserve banks, who by the way also print all the paper currency. So having that backstop is important for regular banks to have the power to create money, but the actual creation of money happens digitally to begin with, regardless of whether the bank later needs to distribute paper bills or borrow from the federal reserve.