Paging in Dashboard>Appearance>Menus>Categories>View All not working

It’s not a known bug but is specific to your site. Can you replicate the problem using the default 2012 theme with all plugins deactivated?

I will try to do that but don’t know yet when I will have time. Not being an expert, like you, it seems like a lot of time and work.

There is no magic bullet in these situations. This is just the start of basic troubleshooting and is a process of elimination deliberately designed to locate the root cause as quickly as possible by first removing the most obvious and common culprits via a series of (often) temporary steps.

Do you want to locate and, hopefully, fix the problem on your site? If “yes”, then please help us to help you and carry out the changes that we suggest. Sorry to be so blunt but there are no other options that we can offer you.

Nothing wrong with blunt as long as clarity goes with it. If I hadn’t already found a work-around, I might want to pursue it. I’ve reported it and I’m done with it for now.