can assignTimestampAndWatermark again on a watermarked table？
I’m afraid not, multiple watermark statements is not supported yet,
If you need multiple watermarks for one table, you can simply create
multiple tables with different watermark using DDL in you catalog.
You can create a new table based on the existing table using LIKE syntax  in the upcoming 1.11 version, e.g.
CREATE TABLE derived_table (
WATERMARK FOR tstmp AS tsmp - INTERVAL '5' SECOND
) LIKE base_table;
For now, maybe you have to manually create a new table using full DDL.
is it possible to define WATERMARKS in SQL queries/views? We have a read only catalog implementation and we would like to assign WMs to the tables somehow.