Custom yearly source index
First activate FacetWP. Then activate FacetWP - Yearly to create your yearly facet.
Create a Facet, for example a Select Facet, and choose "Yearly archive" as Data source.
By default, years are sorted by chronological order. If you want to reverse this order, you can use this snippet :
add_filter( 'facetwp_facet_orderby', 'sort_yearly_desc', 10, 2 );
function sort_yearly_desc( $orderby, $facet ) {
if ( 'YOUR_FACET_NAME' === $facet['name'] ) {
$orderby = 'f.facet_display_value DESC';
}
return $orderby;
}