Trying to input an opening Retained Earnings figure in Sage Business Cloud Accounting

Afternoon all, 

Last year, we moved our internal profit & loss reporting to the Sage Business Cloud Accounting system, taking 01/01/2020 as our commencement date. We manually input all the various customer/supplier opening balances, invoices, and banking transactions, and almost everything is working swimmingly. 

We're just at the point now where we're tidying up our balance sheet report, and I noticed that by default, there are no Equity nominals in the Chart of Accounts, and the Balance Sheet Report only includes Profit/Loss from the current year (2021) and the prior year (y/e 31/12/2020). 

I want to take the Retained Earnings figure from the published accounts we sent into the Companies House for y/e 31/12/2019 and input this figure into the new system. So far, the only solution I can think of is to create a 'Retained Earnings' nominal in the Chart of Accounts, and enter the figure via either an Opening Balance or a journal, then manually adjust that figure every year. Is there a more elegant/automated solution that would automatically integrate the opening Retained Earnings figure with each passing year's profit (see screenshot below from the existing Balance Sheet report)?