Hello, I need more information on this.

On bookmarks toolbar, every item is preceded by an unwanted graphic that simply takes up room; how does one get rid of them? On other toolbars, items are now (Firefox57) represented by icons that one has to hover over to get an explanation; I prefer text.

In addition, I like tabs on the bottom row, under the other toolbars; how do I move toolbars into the order I prefer?

Heres how to move tabs on the bottom row: https://www.youtube.com/watch?v=3Xo-OeVjnjs

The answer to all of these questions is "custom style rules in a userChrome.css file" because extensions no longer can make significant changes to the toolbar area. What's a userChrome.css file? See: https://www.userchrome.org/what-is-userchrome-css.html

(1) On bookmarks toolbar, every item is preceded by an unwanted graphic that simply takes up room; how does one get rid of them?

.bookmark-item .toolbarbutton-icon {
  display: none !important;
}

(2) On other toolbars, items are now (Firefox57) represented by icons that one has to hover over to get an explanation; I prefer text.

I'm going to look into how to do this.

(3) In addition, I like tabs on the bottom row, under the other toolbars; how do I move toolbars into the order I prefer?

You can download this file as an example: https://www.userchrome.org/samples/userChrome-tabs_on_bottom.css

jscher2000 said

(2) On other toolbars, items are now (Firefox57) represented by icons that one has to hover over to get an explanation; I prefer text.

I'm going to look into how to do this.

Here is an example of a custom style rule you could use:

/* Hide Icons on Main Toolbar */
#nav-bar .toolbarbutton-1:not([skipintoolbarset]) .toolbarbutton-icon, 
#PanelUI-menu-button .toolbarbutton-badge-stack {
  width: 0 !important;
  padding: 0 !important;
  margin: 0 !important;
}
/* Show Text Labels on Main Toolbar */
#nav-bar .toolbarbutton-1:not([skipintoolbarset]) .toolbarbutton-text {
  display: -moz-box !important;
  font-size: 14px !important;
  padding: 4px !important;
}
#downloads-button .toolbarbutton-badge-stack, 
#downloads-indicator-anchor, #downloads-indicator-icon, 
#downloads-indicator-progress-outer, #downloads-indicator-progress-inner {
  display: inline-block !important;
  width: 0 !important;
  min-width: 0 !important;
  padding: 0 !important;
}

You would create a userChrome.css file and paste that in. I created a website to help with the project of creating and editing a userChrome.css file. In case you need details for that:

https://www.userchrome.org/how-create-userchrome-css.html

I also saw an icon + text layout from the author of Classic Theme Restorer: https://github.com/Aris-t2/CustomCSSforFx/blob/master/classic/css/toolbars/toolbar_mode_icons_and_text.css

Sorry to take so long to get back to you -- your suggestions worked just fine. Now if Classic Theme Restorer comes up with some nice tab variations and colors, I'll be all set.