Still working, very good!

Can't believe that it's 9 years since it was published and there's still no way to merge taxonomy in WordPress core. They found time to add all the bells and whistles, even Gutenberg not demanded by anybody, but such and obvious and needed function is still absent. Actually I was rather lucky that i found the plugin cause it's buried in the deepest end of plugins section and even if you copy/paste it's name you'll have to scroll down a few pages. It's crazy! Hope WordPress developers won't brake it with some update... !!! Take notice this plugin does not swap attribute terms selected for variations, so after attributes merge you'll have to readd them manually

As far as I can tell, this is still working fine with Still Works with woocommerce 3.6.2

Re-categorizing thousands of posts from the past six years seemed like an insurmountable task, but I kept coming across this old plugin being recommended for just that task. I made a fresh backup of my site, (just in case), installed the plugin and VIOLA! What would have literally taken me hours and hours of repetitive work changing the category of each post was accomplished within seconds with this plugin. I'm running 5.1.1 and the plugin, while very old, worked flawlessly.

Just used in my 4.9.8 copy, the set parent for the custom categories is working like a charm. I haven't tested other option yet. It is already helpful to me.

As others have said, this still works well, no regular updates needed when sth is well programmed from the outset, DEAR WP MODS! Thank you scribu!!