My VSCode Custom CSS

custom.css

.monaco-shell {
  font-family: "Fira Code", "Inconsolata", monospace;
}

/* This makes the dirty tab circle yellow */
.vs-dark
  .monaco-workbench
  > .part.editor
  > .content
  > .one-editor-silo
  > .container
  > .title
  .tabs-container
  > .tab.dirty
  .close-editor-action {
  background: url("data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' height='16' width='16'%3E%3Ccircle fill='%23ffc600' cx='8' cy='8' r='4'/%3E%3C/svg%3E")
    50% no-repeat;
}

.monaco-workbench > .editor > .content > .one-editor-silo {
  border-top: 1px solid #15232d !important;
}

.one-editor-silo + .one-editor-silo {
  border-left: 1px solid #15232d !important;
}

/*
  This puts a thin yellow border around the found items like Sublime did it
*/
.monaco-editor .findMatch,
.monaco-editor .selectionHighlight {
  border: 1px solid #ffc600;
  border-radius: 2px;
  background: transparent;
}

/* This accounts for larger font cutting off - bump up 3px */
.monaco-workbench>.activitybar>.content .monaco-action-bar .badge .badge-content {
  top: 17px !important;
}

.monaco-workbench .tabs-container .tab * {
  font-style: italic;
}