What icon are you talking about?

Customize Firefox controls, buttons and toolbars {web link}

Type about:customizing<enter> in the address bar.

Note: about:customizing is no longer present in Firefox 47+ releases.

• Press Alt or F10 to bring up the Menu Bar.Then View > Toolbars > Customize.
• Right-click on a blank spot in the toolbar and select Customize.

In the new window, look for the icon. When you find it, hold down the left button on it, and move it to where you want it to be. You can move any of the icons you want from here, but; some icons are locked in place.

There is also a Restore Defaults button at the bottom right.

i need to remove (+) on my exit, minimize, restore down. in my file manager there is no + icon, but in firefox there is a + icon in my exit bar (pict 1 my file manager, pict 2 mozilla firefox)

If you are talking about the + that opens a new tab, does my last post work on it?

If you are talking about the + that opens a new tab, does my last post work on it?

not in new tab, but in exit, minimize, and restore down. im use a mozilla in linux

sandhyzidan said

not in new tab, but in exit, minimize, and restore down. im use a mozilla in linux

Not sure what Linux and window manager you are using however with ones like XFCE you can change position of buttons and remove/add buttons on titlebar in window manager style settings.