Is it possible to change a primary key to be auto_increment in an existing table?

Embedded Firebird Db, LO Base 6.2 running on Ubuntu 18.04

In the base overview choose “tables”. Right-click on the desired table. Select Edit ....
In the editable table, mark the corresponding field. Select Yes at “AutoValue”.
Save the table and save the DB.

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With me Windows 10 Home; Version 1903; 64-Bit | LibreOffice, Version: (x64).

I find that does not work in Firebird: at least not in my case.
I have actually managed to straighten myself by using a backup from before I broke things, and doing a lot of copy and paste after that. (Had to straighten it out: it’s my wife’s data, and one must stay onside OR ELSE THERE WILL BE CONSEQUENCES!)