You can add as many accounts as you like. Adding all of your accounts (including things like mortgages) is a nice way to get an overview of all your finances.
Actual makes a distinction between accounts being for budget or off budget. Off budget accounts don't effect the budget and are meant to track stuff like investments and mortgages. Transactions in off budget accounts can't be categorized; they simply track balances over time.
For budget accounts affect the budget, and transactions can be categorized. These are accounts where you want to track cash flow and use the budget, like checking accounts and credit cards.
Depending on your usage, savings accounts can either be on or off the budget. If you're not sure, we recommend keeping it off the budget at the start.
You can still access this account under Closed Accounts in the sidebar, and even reopen it from the same actions menu.
If you want to delete an account even if it has existing balances, in the popup after selecting Close Account, click the force close at the bottom.