What panel do you mean? Is that the left panel that shows a tree list of all folder or the toolbar at the top?

You can consider to use the sidebar to only get one list of the bookmarks.

You can add the "Bookmarks Menu" button that shows the bookmarks in a drop-down list to the Navigation Toolbar via these steps:

• click the bookshelf icon on the Navigation Toolbar or alternatively use the Library menu in the "3-bar" Firefox menu button drop-down list
• click Bookmarks
• click "Bookmarking Tools", then click "Add Bookmarks Menu to Toolbar"

The Bookmark Menu button should appear on the Navigation Toolbar.

You can also drag the Bookmarks Menu button from the Customize palette to the Navigation Toolbar

See also "How do I add the Bookmarks Menu button to the toolbar?":

• https://support.mozilla.org/en-US/kb/bookmarks-firefox#firefox:win10:fx57

Again, I am asking about the Library window, not the Browser itself or anything in the browser window (e.g. Bookmark button, ...).

There doesn't seem to be the functionality to show or unshow the left side-bar panel in the Library window.

And, I could not find anything that addresses this issue in the forum. So, I was wondering if anyone knows of a way to turn the panel on/off.

If it is possible and you would hide this panel then you won't be able to navigate up in the tree as there is no way to go to the parent folder via the right pane, you can only open sub folders. The sidebar allows to navigate, that is why I posted that as an alternative.

This code in the Browser Console toggles that left tree pane for me.

• https://developer.mozilla.org/en/Tools/Browser_Console

var wm = Services.wm;
var doc = wm.getMostRecentWindow("Places:Organizer").document;
var pll = doc.getElementById("placesList");
var pld = doc.defaultView.getComputedStyle(pll,"").getPropertyValue("visibility");
pll.style.setProperty("visibility",(pld=="visible")?"collapse":"visible","");
pld = pll.style.getPropertyValue("visibility");
pld

Wow! I was thinking maybe I was missing a visual button or something.

I've never used the Browser Console before (actually I didn't even know where it was until a few moments ago). Found it on the browser, under menu item Tools--Web Developer.

Your mention about "toggle" is something I would like, because there are times when the tree items definitely need to be used. However, when I keep the Library window open (to have easier access to the files I downloaded), the tree panel is not needed for use. And being able to collapse it or hide it would allow better use of screen placement.

I'd like to try-out the code you kindly supplied, but after looking at the Browser Console, I'm not sure how to proceed -- for now.

The link you included has some good info. As time permits, I will endeavor to understand more. Not being familiar with the Web Console, will also be an inhibiting factor for me.

Thanks for your efforts to help.

Finally ran the code, but got the following at the bottom of the console:

ReferenceError: Services is not defined

But at least nothing else seemed to go hair-wire.

Ran the code again, and this time there were no error msgs. And the Library window's tree panel disappeared as desired.

Also, this time I ran the code in a New Tab. Was that supposed to make a difference?

If you would, please send the code to restore the panel back to visible, so I don't have to restart the browser each time.

Thanks. Please let me know.

The code works as a toggle (visibility: collapse|visible), so you only have the run the code another time to get the panel back and repeat if you want to hide again. You can use cursor UP key to recall the code from the command line history and press the Enter key to run the code, so no need to paste a second time.

OK, yes it does! Thanks again.

So .. did the New Tab make a difference somehow? If so, in what way?

The new tab shouldn't make a difference for the Browser Console. Maybe you opened the Web Console the first time. The code I posted only works in the Browser Console (Shift+Ctrl+J) and not in the Web Console.

OK, humble thanks for your expertise, Top Contributor!!