change the vertical order of [tab|address|bookmark] bars

I've previously changed userChrome.css to have tabbar at the bottom of the toolbars, as explained in https://support.mozilla.org/it/questions/1186247. But now, after having updated FF from 60ESR to 68, I end up with the tabbar on the top, again. Googling for "-moz-box-ordinal-group" I get https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-box-ordinal-group where I read "Warning: This is a property of the original CSS Flexible Box Layout Module draft, and has been replaced in newer drafts." How can I restore my preferred layout (tabbar on the bottom) through userChrome.css? Thanks.