Adding Sub Categories Widget's funcationality to template

I am working on a website where this widget would work well from a functionality perspective.

The subcategory dropdown would however need to be included in the template or post content from a usability standpoint.

I searched through this forum; it looks like the topic of adding this “widget” to the template was discussed here about three years ago. There has been no discussion off late.

Is it possible to add the Sub Categories Widget’s functionality to a template now?

If not possible right out-of-the box, how would one go about adding the widget’s functionality to a template?

I would appreciate suggestions.

Thanks,
Melissa

https://ww.wp.xz.cn/plugins/sub-categories-widget/