One way you can do this is to store the value of the "tableau_url" in a text file, and then create a new Delimited file data source with that file. That file would have just one line in it, the URL you need on that server, for example on Dev:
Then create a base view on this new data source. For example the new base view could be called **bv_tableau_url_data**.
Then create a new Join derived view from this new base view, and your existing derived view. Add a new field that uses the base view's **bv_tableau_url_data.Column0** in the field expression.
Then you only need to update the contents of the Delimited file on each server. This also makes it easy to change the URL in the future, and also this option could be expanded to add more configurable values to the Delimited file and base view if needed.
Hope this helps!