I am facing an issue trying to find a way to insert some computed rows into a table in the context of a dlt pipeline.

My use case is extremely simple. Moving from bronze to silver I update several tables using a mix of streaming and materialized tables. I need also to write some rows into a silver table. I do not have a stream source to read as the rows are computed/aggregated. I tried the append_flow but that expects a stream source that I cannot provide. Using once=true works but as the param says it works only once. 

It seems extremely weird that DB does not support a so simple use case. Am I missing something?