Copy a development library as the starting point for another development library

[#1]

At the moment the starting point for any new library is the 'upstream resources'.  However, we are finding situations where we want to use a library that is in development as the starting point.  The only way to achieve this seem to be to recreate the setup of the other library by manually selecting the same revisions - unfortunately, this is time consuming and prone to error 😞

Please can you consider introducing an option to 'copy' a library in development to use as the starting point for a new library?