Rounded VS Code Tabs

custom.css

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container {
  padding-left: 22px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab {
  border-radius: 5px 5px 0 0;
  height: 28px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab + .tab {
  margin-left: 16px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab:before {
  content: '';
  position: absolute;
  left: -18px;
  top: -1px;
  border-right: 0;
  margin: 0;
  padding: 0;
  width: 30px;
  border-radius: 5px 0 0 0;
  height: 28px;
  border-left-color: rgb(37, 37, 38);
  border-right-color: rgb(37, 37, 38);
  background-color: rgb(22, 26, 27);
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab.active:before {
  background-color: rgb(28, 32, 34);
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab.active {
  z-index: 1;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab .tab-label, .monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .title-label {
  position: relative;
  left: -16px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab>.tab-close {
  position: relative;
  left: -4px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title, .monaco-workbench>.part>.title {
  height: 28px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container {
  height: 28px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .editor-actions .action-label, .monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .title-actions .action-label {
  height: 28px;
  line-height: 28px;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .monaco-icon-label:before {
  height: 28px;
  vertical-align: middle;
}

.monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .tabs-container>.tab .tab-label a, .monaco-workbench>.part.editor>.content>.one-editor-silo>.container>.title .title-label a {
  font-size: 11px;
  vertical-align: top;
}