Sorry, that's not the best possible advice. appserver_autoexec gets called way too often in many other situations and you may not want the library to be assigned every time.
The intended solution is to add this library definition into sashome/9.4/SASFoundation/sasautos/mausrexp.sas script. Read the comments there carefully and follow the example provided. It needs to be some macro variable definition, not just a plain libname statement.
P.S> It's definitely a disappointing gap in the product that it requires you to go this far around, rather than automatically and cohesively assigning the library from the metadata definition.
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Dmitriy Alergant, Tier One Analytics