left: 100% to move the popout menu to the right of the parent.visibility: hidden to hide the popout menu initially, allowing for transitions to be applied (unlike display: none).:hover, :focus and :focus-within pseudo-class selectors to apply visibility: visible to the popout menu, displaying it when the parent element is hovered/focused.<div class="reference" tabindex="0"> <div class="popout-menu">Popout menu</div> </div>
.reference {
  position: relative;
  background: tomato;
  width: 100px;
  height: 80px;
}
.popout-menu {
  position: absolute;
  visibility: hidden;
  left: 100%;
  background: #9C27B0;
  color: white;
  padding: 16px;
}
.reference:hover > .popout-menu,
.reference:focus > .popout-menu,
.reference:focus-within > .popout-menu {
  visibility: visible;
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