code-lab/node_modules/vuetify/lib/components/VTabs/VTab.css

.v-tab.v-tab.v-btn {
  height: var(--v-tabs-height);
  border-radius: 0;
  min-width: 90px;
}
.v-slide-group--horizontal .v-tab {
  max-width: 360px;
}
.v-slide-group--vertical .v-tab {
  justify-content: start;
}

.v-tab__slider {
  position: absolute;
  bottom: 0;
  left: 0;
  height: 2px;
  width: 100%;
  background: currentColor;
  pointer-events: none;
  opacity: 0;
}
.v-tab--selected .v-tab__slider {
  opacity: 1;
}
.v-slide-group--vertical .v-tab__slider {
  top: 0;
  height: 100%;
  width: 2px;
}