See https://streamable.com/b6e4p0 for a video showing the behaviors.

discord_collapse_sidebar.css

/* See https://streamable.com/b6e4p0 for a video showing the behaviors. */

.bd-minimal .sidebar-2K8pFh {
  width: 50px !important;
  transition: width .05s ease-in;
}

.bd-minimal .sidebar-2K8pFh h2 {
  display: none;
}

.bd-minimal .sidebar-2K8pFh .channel-2QD9_O[href="/channels/@me"], 
.bd-minimal .sidebar-2K8pFh .channel-2QD9_O[href="/library"], 
.bd-minimal .sidebar-2K8pFh .channel-2QD9_O[href="/store"],
.bd-minimal .sidebar-2K8pFh .searchBar-6Kv8R2 {
  display: flex;
  margin-left: 0px;
}

.bd-minimal .sidebar-2K8pFh .avatar-3uk_u9 {
  margin-left: 5px;
  margin-right: 0px;
}

.bd-minimal .sidebar-2K8pFh:hover .channel-2QD9_O[href="/channels/@me"], 
.bd-minimal .sidebar-2K8pFh:hover .channel-2QD9_O[href="/library"], 
.bd-minimal .sidebar-2K8pFh:hover .channel-2QD9_O[href="/store"] {
  display: inline-block;
  margin-left: 8px;
}

.bd-minimal .sidebar-2K8pFh:hover {
  width: 250px !important;
  transition-timing-function: ease-out;
}

.bd-minimal .sidebar-2K8pFh:hover h2,
.bd-minimal .sidebar-2K8pFh:hover .searchBar-6Kv8R2 {
  display: flex;
}

.bd-minimal .sidebar-2K8pFh:hover .avatar-3uk_u9 {
  margin-left: 0px !important;
  margin-right: 12px !important;
}

.bd-minimal .sidebar-2K8pFh .children-3rEycc {
  display: none;
}

.bd-minimal .sidebar-2K8pFh:hover .children-3rEycc {
  display: flex;
}

Yo, thanks for this!

Do you think it would be possible to make it toggle-able with a keybind, instead of auto-hide?