@Michel-AUBINEAU ,
Are these settings specific to the application or are they related to the document I’m working on?
The “Theme” (Settings > Style Configurator > Select Theme) and “icon” settings (Settings > Preferences > General, in the Toolbar section) are remembered in the Notepad++ settings, and are global to Notepad++, not specific to individual files – so all files opened in Notepad++ will use the same theme and icon choices.
Notepad++ saves your choice when you exit Notepad++ after setting the Theme or Icon, and the next time you run Notepad++ it will use those same Theme and Icon settings.
If you believe that it is not remembering the Theme and Icon settings correctly when you restart Notepad++, then either you do not have write permission on your configuration files (check permissions on files in %AppData%\Notepad++\ for a normal installation); or you had multiple instances of Notepad++ open, and the last one to save its settings was still using the old Theme or Icon settings so that’s what got saved; or you have multiple copies of Notepad++ installed , and you are changing the settings on one copy of Notepad++ and then are surprised that another copy has different settings (like maybe one in C:\Program Files\Notepad++ which uses %AppData%\Notepad++ for its settings, and another portable copy unzipped in D:\myPortable\Notepad++ which stores its settings in the installation directory).
addition:
To verify the last idea: set your theme and icons as you want, and copy the info from ?-menu’s Debug Info and paste into your reply; then exit Notepad++ and restart the application: if the Theme and Icons went back to the original settings, then copy ? > Debug Info again. Paste both versions of Debug Info into your reply, and we can see if we see anything that tells us what’s wrong; otherwise, it will at least confirm which directory you should be looking in for the permissions
Also, a fourth idea is that you are sometimes running in Administrator mode (the Title bar for Notepad++ will say “Administrator” and the Debug Info will say “Admin Mode: ON”) and sometimes as your normal user. It may be that the Admin Mode version is using a different set of preferences than the normal-user version.