zen-desktop/src/browser/base/content/zen-styles/zen-workspaces.css

#zen-workspaces-button {
  border: 1px solid var(--zen-colors-border);
  border-radius: var(--zen-button-border-radius);
  min-height: 33px;
  justify-content: center;
  align-items: center;
  display: flex;
  box-shadow: rgba(0, 0, 0, 0.05) 0px 1px 2px 0px;
}

#zen-workspaces-button .zen-workspace-sidebar-name {
  margin-left: 0.2rem;
  display: none;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  font-size: 12px;
}

@media (-moz-bool-pref: 'zen.view.sidebar-expanded') {
  /** Keep these selectors in sync with the ones in vertical-tabs.css */
  #navigator-toolbox:is(
      #navigator-toolbox[zen-user-hover='true']:hover,
      #navigator-toolbox[zen-user-hover='true']:focus-within,
      #mainPopupSet[zen-user-hover='true']:has(> #appMenu-popup:hover) ~ toolbox,
      #navigator-toolbox[zen-user-hover='true']:has(*[open='true']:not(tab):not(#zen-sidepanel-button)),
      :not([zen-user-hover='true'])
    ) {

    & #zen-workspaces-button {
      width: calc(var(--zen-sidebar-action-button-width) - 1px) !important;
      margin-top: .2rem;
      height: calc(var(--zen-sidebar-action-button-width) - 10px) !important;
    }
    
    & #zen-workspaces-button .zen-workspace-sidebar-name {
      display: block;
    }

    & #zen-workspaces-button .zen-workspace-sidebar-icon[no-icon='true'] {
      display: none;
    }

    & #zen-workspaces-button .zen-workspace-sidebar-icon[no-icon='true'] + .zen-workspace-sidebar-name {
      margin-left: 0;
    }

    & #zen-workspaces-button {
      overflow: hidden;
      white-space: nowrap;
      text-overflow: ellipsis;
      display: flex;
      padding: 2px 10px;
      width: calc(100% - var(--zen-tabbrowser-padding) * 6) !important;
      gap: 0.5ch;
    }
  }
}

/* Workspaces Panel UI */

#PanelUI-zen-workspaces {
  --panel-width: 320px;
  --panel-padding: 0;
}

#PanelUI-zen-workspaces > panelmultiview {
  align-items: flex-start;
  overflow-x: hidden;
  overflow-y: auto;
}

#PanelUI-zen-workspaces panelmultiview panelview {
  position: relative;
  padding: 15px;
  width: var(--panel-width);
  min-height: 150px;
}

#PanelUI-zen-workspaces-create-input,
#PanelUI-zen-workspaces-edit-input {
  margin-top: 10px;
}

#PanelUI-zen-workspaces-create-icons-container toolbarbutton,
#PanelUI-zen-workspaces-edit-icons-container toolbarbutton {
  width: 30px;
  height: 30px;
  display: flex;
  justify-content: center;
  align-items: center;
  border: 2px solid transparent;
  border-radius: 7px;
}

#PanelUI-zen-workspaces-create-icons-container toolbarbutton[selected='true'],
#PanelUI-zen-workspaces-edit-icons-container toolbarbutton[selected='true'] {
  border-color: var(--zen-colors-secondary);
}

#PanelUI-zen-workspaces-create-icons-container toolbarbutton .toolbarbutton-icon,
#PanelUI-zen-workspaces-edit-icons-container toolbarbutton .toolbarbutton-icon {
  display: none;
}

#PanelUI-zen-workspaces-create-icons-container toolbarbutton .toolbarbutton-text,
#PanelUI-zen-workspaces-edit-icons-container toolbarbutton .toolbarbutton-text {
  min-width: unset;
}

#PanelUI-zen-workspaces-create-icons-container,
#PanelUI-zen-workspaces-edit-icons-container {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(30px, 1fr));
  gap: 8px;
}

#PanelUI-zen-workspaces-create-icons-container toolbarbutton.toolbarbutton-1,
#PanelUI-zen-workspaces-edit-icons-container toolbarbutton.toolbarbutton-1 {
  margin-top: 10px;
}

#PanelUI-zen-workspaces-list {
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
}

#PanelUI-zen-workspaces-list[empty='true'] {
  font-weight: 600;
  padding: 10px;
  width: 100%;
  text-align: start;
  opacity: 0.5;
}

#PanelUI-zen-workspaces-current-info toolbarbutton:last-child {
  margin-bottom: 0 !important;
}

#PanelUI-zen-workspaces-list toolbarbutton,
#PanelUI-zen-workspaces-current-info toolbarbutton {
  padding: 5px;
  border-radius: var(--zen-button-border-radius);

  margin-left: 0 !important;
  margin-right: 0 !important;

  display: flex;
  align-items: center;

  &:first-child {
    margin-top: 10px;
  }

  & .zen-workspace-icon {
    width: 30px;
    height: 30px;
    border-radius: var(--zen-button-border-radius);
    margin-right: 10px;
    border: 1px solid var(--zen-colors-border);
    display: flex;
    justify-content: center;
    align-items: center;
    font-weight: 600;
    flex-shrink: 0;
  }

  &[data-usercontextid] .zen-workspace-icon {
    border-color: color-mix(in srgb, var(--identity-tab-color) 40%, transparent 60%);
  }

  & .zen-workspace-name {
    font-weight: 600;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }

  & .zen-workspace-container {
    font-size: 12px;
    opacity: 0.5;
    font-weight: normal;
  }

  & .zen-workspace-actions {
    display: none;
    margin: 0;
    margin-left: auto !important;
  }

  &:hover .zen-workspace-actions,
  & .zen-workspace-actions[active='true'] {
    display: flex;
  }
}

#PanelUI-zen-workspaces-current-info toolbarbutton:first-child {
  margin-bottom: 10px;
  margin-top: 5px;
}

#PanelUI-zen-workspaces-view > vbox:nth-child(2) {
  margin-top: 10px;
}

#PanelUI-zen-workspaces-new {
  margin-left: auto;
  min-height: 1px !important;
  padding: 3px;
  border-radius: 4px;
  width: 20px;
  height: 20px;
}

#PanelUI-zen-workspaces-create-footer,
#PanelUI-zen-workspaces-edit-footer {
  padding-bottom: 0 !important;
  margin-top: 10px;
  margin-left: 0;
  margin-bottom: 0 !important;
  width: 100%;
}

#PanelUI-zen-workspaces-create-footer button[default='true'],
#PanelUI-zen-workspaces-edit-footer button[default='true'] {
  width: 100%;
}