calm-twitter.css

/* Removes items from the left-hand menu */
div[aria-label="Top Tweets off"],
[data-testid="AppTabBar_Explore_Link"],
a[href="/i/bookmarks"],
a[href$="/communities"],
[data-testid="AppTabBar_More_Menu"],
[data-testid="SideNav_NewTweet_Button"],

[data-testid="sidebarColumn"],  /* right-hand "explore" column */
[data-testid="DMDrawer"], /* Messages drawer */
[data-testid="cellInnerDiv"] > div > div > [data-testid="placementTracking"], /* Promoted tweets */
[data-testid="app-text-transition-container"], /* Retweet, like, ... counts */
nav[aria-label="Profile timelines"], /* Profile nav: Tweets, Tweets and replies, ...*/
a[href*="/following"], /* Profile: Following count */
a[href*="/followers"], /* Profile: Follower count */
[data-testid="UserProfileHeader_Items"] > span:last-child /* Profile: Joined...  */ {
  display: none !important;
}