Hello.
1. Sorry for my belated reply. Over the holiday season I tested the use of the INKSCAPE_PROFILE_DIR environment variable. Success!
How? Add this line to the "User Variables" section of Windows environment variables:
-- INKSCAPE_PROFILE_DIR=D:\INKSCAPE
(or whatever custom path you wish)
After the change, log out then log back in.
2. However, please note that a custom path for this variable only impacts these three items in the System | System Info preferences:
-- User Config
-- User Preferences
-- User Extensions
BEFORE - (default) path: C:\Users\<user_name>\AppData\Roaming\
AFTER - (custom) path: D:\Inkscape\
3. Also note that you need to log in with Windows Administrator privileges. As an admin you can take this route to access the dialog box for editing the environment variables:
-- System | Advanced System Settings | Advanced | Environment Variables
4. If you do not have admin privileges you can try this free small tool, Rapid Environment Editor, which I have used frequently with different Windows versions:
--
https://www.rapidee.com/en/download5. Hope this helps another Inkscape user.