QCAD2 offered the user to specify in the program settings where these directories should be/go, and took the first one in each list as default; QCAD3 only offers to enter auxiliary library and template directories and has no provisions for defaults.

All associated data (scipts, templates, libraries, patterns, fonts) is stored under the program directory, exactly where it should not be. Windows 7 and higher default prevent modifying the programs directory by redirecting the writes.
An extra user-input during the Windows install process would be in order.

QCAD3 should offer the user to specify any and all data directories involved (including the auto save), and make it possible to specify a default for each.
This list could be initialised with the installation defaults, or default to the installation directories when empty.