The unnecessarily oversized buttons atop the Direct Messages page were bugging me, so I made this. It resizes the entries to be roughly the same size as channel list entries, thus giving more space for the actually important stuff below.
EDIT: Added another line to account for message requests as well.
/* Smaller DM page top buttons */
a[data-list-item-id$="_friends"],
a[data-list-item-id$="_library"],
a[data-list-item-id$="_messageRequests"],
a[data-list-item-id$="_nitro"],
a[data-list-item-id$="_shop"],
a[data-list-item-id$="_quests"] {
padding-top: 3px !important;
padding-bottom: 3px !important;
}
Before and after: