create hide_tabs_scrollbuttons.css

chrome/hide_tabs_scrollbuttons.css

@@ -0,0 +1,20 @@
+/* Source file https://github.com/MrOtherGuy/firefox-csshacks/tree/master/chrome/hide_tabs_scrollbuttons.css made available under Mozilla Public License v. 2.0
+See the above repository for updates as well as full license text. */
+
+/* This should hide tabs scrollbuttons in a manner that preserves the ability to move tab strip when reordering tabs */
+
+#tabbrowser-tabs:not([movingtab]){ --uc-scroll-visibility: hidden }
+#tabbrowser-tabs[overflow]{ --uc-scrollbox-margin: -28px }
+
+#scrollbutton-up{ position: relative;z-index: 1 }
+
+#scrollbutton-up,
+#scrollbutton-down,
+#scrollbutton-up ~ spacer{
+  visibility: var(--uc-scroll-visibility,visible);
+}
+.scrollbox-clip{ margin-inline: var(--uc-scrollbox-margin,0); }
+#tabbrowser-tabs[overflow][positionpinnedtabs] .tabbrowser-tab[pinned]{
+  border-left: 28px solid transparent !important;
+  clip-path: padding-box
+}

html_resources/tagmap.json

@@ -117,5 +117,6 @@
 "window_control_fallback_for_custom_windows_theme.css":["window-controls","buttons","colors","patch"],
 "window_control_placeholder_support.css":["window-control","patch"],
 "buttonlike_toolbarbuttons.css":["buttons"],
-"passive_tab_audio_label.css":["tab","proton"]
+"passive_tab_audio_label.css":["tab","proton"],
+"hide_tabs_scrollbuttons.css":["tabs","hiding","buttons","minimal"]
 }

tags.csv

@@ -117,3 +117,4 @@ window_control_fallback_for_custom_windows_theme.css,window-controls,buttons,col
 window_control_placeholder_support.css,window-control,patch
 buttonlike_toolbarbuttons.css,buttons
 passive_tab_audio_label.css,tab,proton
+hide_tabs_scrollbuttons.css,tabs,hiding,buttons,minimal