That’s not possible: in file A you can’t access data from file B (and why would you by the way? Is this by any change related to consolidation files?) .
PS our Silverfin Insights however, could accomplish this, because that’s a function that can read data over all your files (simply put). But then again, this is done on office level and not on file level.
So I’m afraid standard STL can’t help you further in this (on file level that is). Unless you are talking about consolidation files? But even then, the related files can’t be called upon through STL (yet - not sure if this is a generic request for now).
The second part: this has to be done manually by an user OR you could also use our API to fill in the sync-reference of every needed file (but that’s API now, not STL).
We would have liked to do this in order to be able to show all relevant Adsolut data for a physical person/ a company that gets a mandate (‘volmacht’) from a company to do certain things. Now, as this physical person/company is sometimes known by us (in Adsolut) and sometimes not, we would have liked to retrieve all revelant data in the first case.