Вышел Firefox 104.0 | Форум Mozilla Россия

Не, ну автоскрываемая панель из этого комплекта будет работать и в обычном userChrome.css + эта инструкция.
Разве что auto_hide_sidebar.js не будет использован, но это и не особо критично.

Или модифицированный под себя

Выделить код

Код:

@-moz-document url("chrome://browser/content/browser.xhtml") {
#sidebar-box {
    --v-sidebar-min-width: 2px;
    --v-sidebar-min-width-normal: 5px;
    --v-sidebar-max-width: 18em;
    --v-sidebar-transition-delay-show: .1s;
    --v-sidebar-transition-delay-hide: .1s;
    --v-sidebar-transition-duration: .3s;
    /* ********************************************** */

    position: relative !important;
    z-index: 2 !important;
    min-width: var(--v-sidebar-max-width) !important;
    width: var(--v-sidebar-max-width) !important;
    max-width: var(--v-sidebar-max-width) !important;
    overflow: hidden !important;
    opacity: 0 !important;
    --v-sidebar-margin-max-width: calc(-1 * var(--v-sidebar-max-width));
    --v-sidebar-transform-locale-dir: -1;
    --v-sidebar-transform-locale-dir-visible: 1;
    margin-inline-start: 0 !important;
    margin-inline-end: var(--v-sidebar-margin-max-width) !important;
    border: none !important;
    border-inline-end: 1px solid var(--sidebar-border-color, ThreeDShadow) !important;
    transform: translateX(calc(var(--v-sidebar-transform-locale-dir) * (var(--v-sidebar-max-width) - var(--v-sidebar-min-width)))) !important;
    transition-timing-function: linear, step-start !important;
    transition-delay: var(--v-sidebar-transition-delay-hide), calc(var(--v-sidebar-transition-delay-hide) + var(--v-sidebar-transition-duration)) !important;
    transition-duration: var(--v-sidebar-transition-duration), 0s !important;
    transition-property: transform, opacity !important;
}
#sidebar-box[positionend="true"] {
    margin-inline-start: var(--v-sidebar-margin-max-width) !important;
    margin-inline-end: 0 !important;
    border-inline-start: 1px solid var(--sidebar-border-color, ThreeDShadow) !important;
    border-inline-end: none !important;
}
#sidebar-box[positionend="true"]:-moz-locale-dir(ltr),
#sidebar-box:not([positionend="true"]):-moz-locale-dir(rtl) {
    --v-sidebar-transform-locale-dir: 1;
    --v-sidebar-transform-locale-dir-visible: -1;
}
:root[v_vertical_bar_autohide][v_vertical_bar_sidebar="true"] #sidebar-box:not(:hover,[sidebardrag]),
:root[v_vertical_bar_autohide]:not([v_vertical_bar_sidebar]) #sidebar-box:not(:hover,[sidebardrag]) {
    transition-delay: 0s, var(--v-sidebar-transition-duration) !important;
}
:root[sizemode="normal"] #sidebar-box {
    --v-sidebar-min-width: var(--v-sidebar-min-width-normal) !important;
}
#sidebar-box:hover,
#sidebar-box[sidebardrag] {
    transform: translateX(0px) !important;
    opacity: 1 !important;
    transition-delay: var(--v-sidebar-transition-delay-show) !important;
}
:root[v_vertical_bar_visible][v_vertical_bar_start="true"] #sidebar-box:not([positionend="true"]),
:root[v_vertical_bar_visible][v_vertical_bar_start="false"] #sidebar-box[positionend="true"] {
    transform: translateX(calc(var(--v-sidebar-transform-locale-dir-visible) * var(--v-vertical_bar_width, 0px))) !important;
    opacity: 1 !important;
    transition-delay: 0s !important;
}
#browser > #sidebar-splitter {
    display: none !important;
}
#sidebar-box > #sidebar {
    min-width: 0 !important;
    width: auto !important;
    max-width: none !important;
    -moz-box-flex: 1 !important;
}
}
@-moz-document url-prefix("chrome://browser/content/browser.x") {
#sidebar-header {
    height: 46px !important;
    overflow-y: hidden !important;
}
#sidebar-close {
    display: none !important;
}
#sidebar[src^="chrome://browser/content/places/historySidebar.x"] {
    margin-top: -46px !important;
}
#sidebar-switcher-target {
   position: relative !important;
}
}
@-moz-document url-prefix("chrome://browser/content/places/historySidebar.x") {
#search-box {
   display: none !important;
}
#sidebar-search-container {
   -moz-box-pack: end !important;
   height: 46px !important;
   overflow-y: hidden !important;
}
#viewButton {
   position: relative !important;
}
.sidebar-placesTree {
   margin-inline-start: -20px !important;
}
}