Bulk update product category Primary Term to lowest sub-category

Thanks for the feedback.

Primary Category is selected in Titles & Meta > Products > Product Taxonomy
“Show Categories” option is enabled in the breadcrumbs settings

“When you have more than 1 category selected, please choose the one you want to show in the breadcrumbs as “Make term primary””
— this is not possible with 7000+ products

If I’ve understood this correctly, when more than 1 category selected for a product, the following code will automatically assign the taxonomy term from hierarchy root as the Primary Term (i.e not the child term)

add_filter( 'rank_math/frontend/breadcrumb/main_term', function( $current_term, $terms ) {
	return $current_term;
}, 10, 2 );

I’m specifically looking for code to automatically assign Primary Term to the ‘lowest’ child term in the product category hierarchy.

For example, in the following category structure, Guitar Sides should be automatically set as primary term:
Pre-cut Sizes > Instrument Wood > Guitar Sides

Many thanks for the assistance!

Thanks for the suggestion Brian, but in our scenario it isn’t practical as we’re frequently processing bulk product imports with stock changing regularly.

Is there a code solution to achieve this along the lines of the snippet provided, but targeting the lowest product sub-category and not the product root category?

Thanks for the feedback and looking into the query. Understood that pro version is required to access the recommended bulk options tool for completing this process.

Appreciate all the hard work that goes into creating and maintaining such an excellent plugin. Really well done!!