That doesn't work for me, I get the following error:

[PARSE_SYNTAX_ERROR] Syntax error at or near 'GENERATED'(line 2, pos 32).

It sounds like delta lake generated columns have to be based on other columns in the table:

Delta Lake supports generated columns which are a special type of column whose values are automatically generated based on a user-specified function over other columns in the Delta table.

https://docs.databricks.com/delta/generated-columns.html