How would you set up cross-project completion in Kate?

Hi,

The Project tab under Kate settings has a Cross-Project Functionality section, with a couple of checkable settings for Cross-Project Completion and Cross-Project Goto Symbol. It’s right above the Git section in Kate 22.12.3.

Setting up a single project is easy enough, and there are good examples online. I already do it for projects in a number of languages. But how do you set up cross-project completion? I haven’t managed to find anything about it so far except for that section in the settings, and it does nothing as far as I can tell.

Thanks…