Hi Martin,
There is not native functionality in the Asset Leasing module specifically to automatically reverse postings into another layer. As you have pointed out, the guidance does describe a scenario where the Cash Basis layer is reversed out. This is possible by creating the reversing book with accounts mapped to the opposite posting type to essentially reverse out the payments. However, only the Cash Basis books can use this workaround because there are only two accounts the Cash Basis book uses - the Lease Expense and Lease Payment/AP posting types. By creating a book that simply switches the accounts used for these accounts into the Operations layer, this book essentially reverses the postings made into the Current Layer.
The IFRS 16 book presents a more complicated scenario because you cannot simply flip the accounts in the posting types because there are multiple transaction types for each posting type. In other words, there is not a 1:1 relationship between accounts.
In this scenario, what I would recommend is to manually reverse out the entries using the Load Ledger Transactions functionality in the GL.
Navigate to the GL and create an entry in a journal assigned to the Operations posting layer. Select Functions > Load ledger transactions:

In the parameters, the goal is to select filters to bring in the IFRS 16 entries to reverse. Enable the Invert Sign parameter and choose only your IFRS 16 main accounts to reverse, desired posting period, date range, etc in order to bring in only those IFRS 16 transactions for the date range you wish to reverse:

This process should create an entry that reverses into the Operations layer the IFRS 16 entries originally posted in the Current layer. I'd recommend thoroughly testing this approach to ensure it meets your reporting needs and does not disrupt the balances of your existing leases.
Thanks!