@salesforce-ux/design-system/css/menus/submenu/index.css

Salesforce Lightning Design System

/*! Lightning Design System 2.12.0 */
@charset "UTF-8";
.slds-has-submenu {
  position: relative;
}
.slds-has-submenu .slds-dropdown_submenu {
  top: 0;
  -webkit-transform: none;
  transform: none;
}
.slds-has-submenu .slds-dropdown_submenu-left {
  left: auto;
  right: 100%;
  margin-right: 0.25rem;
}
.slds-has-submenu .slds-dropdown_submenu-right {
  left: 100%;
  margin-left: 0.25rem;
}
.slds-has-submenu .slds-dropdown_submenu-bottom {
  top: auto;
  bottom: 0;
  margin-bottom: -0.25rem;
}
.slds-has-submenu.slds-dropdown__item .slds-dropdown_submenu {
  display: none;
}
.slds-has-submenu [role="menuitem"][aria-expanded="true"] + .slds-dropdown_submenu {
  display: block;
}