You don't need to generate opening entries; they are not necessary in Odoo in order to report on the next fiscal year. (That's actually an amazing feature)

The only entry you should do is a manual entry to allocate Current Year Earnings into  Cumulated Earnings.

Here is the full documentation, with advices on how to close the fiscal year; https://www.odoo.com/documentation/user/11.0/accounting/others/adviser/fiscalyear.html