Which desktop file? Do you mean /var/lib/snapd/desktop/applications/chromium_chromium.desktop ? If so that's expected, this file is installed by the snap, you are not supposed to modify it.
You can either override it by copying it to ~/.local/share/applications/ and editing the copy, or alternatively if all you need is to pass additional flags to chromium, you can place a file named ".chromium- browser.init" in your home directory and populate it with: CHROMIUM_FLAGS="--force-dark-mode …" ** Changed in: chromium-browser (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to chromium-browser in Ubuntu. https://bugs.launchpad.net/bugs/1851896 Title: [snap] Changes in desktop file get overwritten Status in chromium-browser package in Ubuntu: Incomplete Bug description: Changes in the chromium_chromium.desktop file get overwritten. This includes flags like --force-dark-mode etc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/chromium-browser/+bug/1851896/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp