Tilda tab style

arc-theme.css

notebook > header {
  background: #f5f6f7;
  border: none;
}
notebook > header > tabs {
  background: transparent;
}
notebook > header > tabs > tab {
  background: transparent;
  color: #8e9195;
  border-radius: 2px 2px 0 0;
  border: 0;
  margin: 0 2px;
  padding: 6px;
  min-width: 100px;
}

notebook > header > tabs > tab:checked {
  background: #ffffff;
  color: #3b3e45;
  border: #dcdfe3 1px solid;
  border-bottom: none;
}

scrollbar {
  background: #fcfcfc;
  margin: 1;
}

style.css

/* ~/.config/tilda/style.css */
GtkWindow#Main {
    #background-color: rgba(0, 0, 0, 0);
    background-color: #000000;
}

GtkWindow#Main .notebook {
    padding: 0px;
}

GtkWindow#Main .notebook tab GtkLabel {
    padding-left: 15px;
    padding-right: 15px;
    padding-top: 5px;
    padding-bottom: 5px;
    color: #999999;
}

GtkWindow#Main .notebook tab {
    background-color: #101010;
    border: 1px solid #222222;
}

GtkWindow#Main .notebook tab:active {
    #background-color: rgba(0, 0, 0, 0.85);
    background-color: #333333;
    border: 1px solid #999999;
}