Hey Handson,
I'm happy to hear you've been part of the QuickBooks Online family for so long! I hope you're enjoying the variety of powerful features designed to simplify your bookkeeping and save you time. If you already know how you'd like to have this recorded, you can easily create an opening balance entry by opening the + New menu and selecting Journal Entry.
Since it sounds like you've been recording transactions that came after this beginning balance, it's crucial to select the appropriate accounts. If you're unsure how to create this journal entry, your accountant is the best person to help. They'll be able to effectively determine the specific accounts and avoid causing issues in your reports. You can easily invite your accountant as a user to approach this together. To search for a pro in your area, simply head to the My Accountant tab in QuickBooks Online then click on Find a pro to help.
Let me know how this goes!