This was discussed in this thread: How to use composite primary key for bulk updates? - #12 by justin
But an official feature request was not made at the time. So I am doing that now.
My particular use case is the join table in a many-many relation. There is no particular reason to create a new ID column or a new column that joins the two primary keys, other than to satisfy Retool's limitation here.
Easy enough for me to add a new column to my database during development, but others may not be so lucky.