src/theme/DocSidebar/Desktop/CollapseButton/styles.module.css

:root {
  --docusaurus-collapse-button-bg: transparent;
  --docusaurus-collapse-button-bg-hover: rgb(0 0 0 / 10%);
}

[data-theme='dark']:root {
  --docusaurus-collapse-button-bg: rgb(255 255 255 / 5%);
  --docusaurus-collapse-button-bg-hover: rgb(255 255 255 / 10%);
}

@media (min-width: 997px) {
  .collapseSidebarButton {
    display: block !important;
    background-color: var(--docusaurus-collapse-button-bg);
    height: 40px;
    position: sticky;
    bottom: 0;
    border-radius: 0;
    border: 1px solid var(--ifm-toc-border-color);
  }

  .collapseSidebarButtonIcon {
    transform: rotate(180deg);
    margin-top: 4px;
  }

  [dir='rtl'] .collapseSidebarButtonIcon {
    transform: rotate(0);
  }

  .collapseSidebarButton:hover,
  .collapseSidebarButton:focus {
    background-color: var(--docusaurus-collapse-button-bg-hover);
  }
}

.collapseSidebarButton {
  display: none;
  margin: 0;
}