I am aware that (at least in the field of economics) typically one first publishes their research as a working paper and later on submits to journals. (Where "later on" could be as short as the same day.)
In our case it so happened that a deadline was tight, and we have now submitted the article to a journal first. While we are waiting for a response from the journal, can we proceed to further prepare and publish our work as a working paper or would such a thing only be appropriate after learning of a negative response from the journal (i.e. only after our paper is no longer considered there)?