Is it possible to set directories prefix wildcards in allowed and disallowed apps? For example if I want to allow any app that has the path prefix of C:\Program Files (x86)\Steam\steamapps\common instead of manually adding each executable and making sure to keep that up-to-date I could add C:\Program Files (x86)\Steam\steamapps\common\* instead.
No, setting directory prefix wildcards in allowed and disallowed apps is generally not supported. However, if you include “C:\Program Files (x86)\Steam\steamapps\common” in the list of allowed apps, it should grant access to all files within that folder.