Hi umpahpah, someone decided that it was not necessary to give a warning if all the tabs you're closing will fit into the "Recently Closed Tabs" list (recently lengthened from 10 to 25 tabs).

You might be familiar with that list from seeing it in one of these places:

• "3-bar" menu button > Library > History > Recently Closed Tabs
• Library toolbar button > History > Recently Closed Tabs
• (menu bar) History > Recently Closed Tabs

I actually preferred the way it was before since it may be annoying to go to that list and re-open a bunch of tabs you didn't intend to close. Unfortunately, I don't know of a way to force a warning.

Maybe someone else knows of one and can help us out here.

Edit: Of course, you can reduce the size of the Recently Closed Tabs list so that you get the warning, but then you're sacrificing some of your ability to re-open closed tabs, so I don't like that option.

Hi Jscher2000,

Thanks for the reply, I checked the Library, but I didn't find settings to reduce number of closed tabs.

And honestly, I do not see a relationship - recently there was a simple option to show or not show the warnings, now it is gone, or at least I can't find it, even in about:config.

Wondering why everything is all the time going for worse, first new engine that killed hundreds of useful add-ons, now this...

These maximums for undo are set via prefs on the about:config page.

browser.sessionstore.max_tabs_undo
browser.sessionstore.max_windows_undo 

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

The history and Library drop down lists merely show a list of recently closed tabs and windows.