Hi Daniel, I don't think there is a setting to disable pinning tabs.

An extension could detect when a tab is pinned and revert it to a normal tab, but your daughter probably would figure that one out, too...

You can give a pinned tab a close button with code in userChrome.css if that is all you need.

Add code to the userChrome.css file below the default @namespace line.

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

.tabbrowser-tab .tab-close-button[pinned] {display:-moz-inline-box!important}

See:

• https://www.userchrome.org/what-is-userchrome-css.html
• https://www.userchrome.org/how-create-userchrome-css.html

In Firefox 69 and later you need to set this pref to true on the about:config page to enable userChrome.css and userContent.css in the chrome folder.

• toolkit.legacyUserProfileCustomizations.stylesheets = true

See:

• https://www.userchrome.org/firefox-changes-userchrome-css.html

Thanks to cor-el for pointing me to userChrome.org !

 This page contained the clue: "Hiding unwanted menu items" - works also in context menus!

Last problem: how to restrict access to the about:config page?

(have Firefox setting managed by an "organization" == me ? )

Best regards Daniel

Keep in mind that you can also pin a tab via the three dot page actions menu. You can even add a pin icon to the location bar via the right-click context menu and there are extensions that allow to pin a tab.

You can use a policy to disable access to about:config.

• https://github.com/mozilla/policy-templates/blob/master/README.md

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-policiesjson
• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig