I can help you with manually adding transactions in QuickBooks Online, @parkerhereautore.
If your online banking is connected to your QBO account, it will automatically download the transactions. Depending on your banking institution, transactions that are older than 90 days will not be included. To add the missing transactions, you can follow the steps outlined below:
Take note that the account register allows you to add transactions directly.
Go to the Gear icon, and select Chart of accounts.
Look for the account register where you want to add the transactions.
Click the View register from Actions column.
Select the Add journal entry, Add check, or Add deposit dropdown menu at the very top of the list.
Choose the type of the transaction you want to add.