In all previous versions, just like in the current one, the creation of a new Account within an Accounts file is accomplished by choosing 'New Account...' from the Account menu, so reverting back won't make a difference here. At this point, there's just the option of exporting the data out and then back into new Accounts that have been added to the original file. For this, open one of the newer Accounts, choose 'Export > Text...' from the File menu, switch back to the original file, create the new Account, and then use 'Import > Text or CSV...' to begin bringing everything in. To view a full walkthrough of the Text Import process (which can be a tad bit tricky, when it comes to getting the Data Layout settings perfect), check out this video tutorial:
https://www.youtube.com/watch?v=hfsJjAic3-A