Is it possible to leave Firefox open when closing its only tab?

Solution 1:

While it isn't possible to keep Firefox open with no tab showing, you can prevent quitting the application when the last tab is closed by having a new tab created automatically (your choice of home page or blank tab). Use about:config to change this behavior.

• In the URL box, type about:config and press Enter.
• If you get a warning that emphasizes "Changing these advanced settings can be harmful...," click the button that says I accept the risk!
• Find the Preference name browser.tabs.closeWindowWithLastTab by typing it in the Search box or copy-and-paste it from here.
• Double-click the Preference to change it to false.