As explained in #1748 (comment), the tab order is currently defined by the element order within the DOM.

If elements are placed in a different visual order, e.g. via display: flex; flex-direction:row-reverse;, then the order may not make sense.

Therefore, there should be a property that allows you to control the general navigation order within a container to focus the elements in visual order, like

nav-order: strutural | visual;

where structural is the default value (behavior the same as defined in the HTML spec.), while visual creates a default navigation order following the visual placement of the ancestor elements considering the writing mode, i.e. for LTR languages the order would be from left to right, for RTL languages from right to left.

Sebastian