Seer that topic to.

https://support.mozilla.org/el/questions/1294519

I try this way but......

I get a similar message on Windows 10:
I don't usually try to save in the root of C:\, but since the Launcher Process was introduced in Firefox 68, I think I have occasionally seen permission messages along these lines. <snip>

I don't think the "You don’t have permission to save in this location" error is related to the Firefox Launcher Process. I get this error on Windows 7 whenever I try to save any file to C:/, even when I open a file in Windows Explorer and go to "File -> Save As". I can get around the Windows Explorer error by disabling User Account Control (UAC).

The error I get in Firefox trying to save a file to C:/ with UAC disabled is "A required privilege is not held by the client. _{This is solved for me by starting Firefox with "C:\Program Files\Mozilla Firefox\firefox.exe" -no-deelevate}

Already tallied why i don't want this solution.

Is there any other way to simply make switch "browser.launcherProcess.enabled" permanent false????

Already tallied why i don't want this solution. Is there any other way to simply make switch "browser.launcherProcess.enabled" permanent false????

You asked about making that preference permanent in your other thread, https://support.mozilla.org/en-US/questions/1294519 Why some switches i change from "about:config" at every firefox update return to default state? and you are getting help there.

You said earlier in this thread that This is not an acceptable solution cause at some pc's I can't modify the shortcut so.......

The Mozilla Support rules and guidelines state, under Posting support requests, Create one thread and only one thread for each subject or Mozilla product you need help with.

Can we keep this thread about why you can't modify the shortcut on some PC's to add the -no-deelevate command line option ... or do you want to use your new thread to continue getting help and close this one?