Firefox 74 is now in the can disable the "Tab tearing" feature that allows drag and drop the tab to a new window.
By open tabs in Firefox separated from the current tab bar, you can bring it into a new window. You can also right-click and "Move to New Window" option is selected under "Move tab" in the context menu. If you find trouble when re-ordering labels or other circumstances, Mozilla now provides a hidden preference settings, you can disable it in the Firefox Nightly. In fact, this problem is emitted from user error reports to complete the repair, it has lasted for nine years.
Disable tab tearing or tab detaching in Firefox
1. Access the about: config
2. In the search box, type "detach" (without the quotes), for the highlighted result, browser.tabs.allowTabDetachthe switching pref value to false.
If you are using Firefox 72, you can install Disable the Detach the Tab Addon . But it is worth noting that, when the Mozilla Firefox about 74: When the config with the above options, the plug may be superfluous.