I’m currently setting up an admin for a clients redesign. There’s going to be a hefty amount of categories and I wanted to make the selector in the sidebar resizable for at least a little bit easier viewing. The simple if not completely cross browser friendly (chrome, ff, safari) way to do this is css’s resize.

/* #talent-categoriesdiv is the .postbox the parent box */
.wp-admin #talent-categoriesdiv .inside{
    /*set an initial height, otherwise it will expand to show all rows*/
    height: 300px;
    resize: vertical;
    overflow: scroll;
}

.wp-admin #talent-categoriesdiv .categorydiv{
    height: 100%
}

.wp-admin #talent-categoriesdiv .tabs-panel{
    height: calc( 100% - 78px );
    max-height: unset;
}

[wp_videojs mp4="https://thisbailiwick.com/wordpress/wp-content/uploads/2018/10/taxonomy-resize.mp4"]