URL

about:config

In console

const name = "Open Link in New Tab";
Services.prefs.setBoolPref(name, true);
console.log(name, Services.prefs.getBoolPref(name));

Open bookmark in new tab: browser.tabs.loadBookmarksInTabs

Settings:

• Open links in tabs instead of new windows (works links that specify a target window)

List:

• open bookmark in new tab: browser.tabs.loadBookmarksInTabs
• open link in new tab: ``

What to do on file link ? Download or open doc

Increase width (size)

widget.non-native-theme.scrollbar.size.override 30

Customize Toolbar to hide the sidebar

https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Bookmark and Browsing History: places.sqlite Cookies: cookies.sqlite Site data (DOM): ``

In snap :

• open troubleshooting
• locate Profile Directory, it should be ~/snap/firefox/common/.mozilla/firefox/<SOME-ID>