Not sure about how to actually add them to the bottom button list, but this explains how to do the things you want in a slightly different way…

Is that the launcher called Application Dashboard? I don’t see a way to do what you’re asking with that one.

The default one in Plasma 5.27 (Application Launcher) makes the leave buttons somewhat configurable. It might be worth a try.

I don’t use Application Dashboard, but on Plasma Drawer if you right click these options, a context menu pops up and allows you to choose what options are presented.

I also use the dashboard.

These three entries are pointlessly redundant, as hitting one of them just brings up the full menu of hibernate/sleep/log out/restart/shutdown anyway, and you have to hit one of them again for it occur immediately. And you can hit a different one from what you used to open it. So you can do shut down>sleep and your PC will sleep because these three basically just open the same real menu… I do not like it.

Alternative: set up keyboard shortcuts for sleep and hibernate.

Personally I configured the power button to sleep instead of shut down, so I just hit that when I’m done at my desktop. I think you can also make the power button open straight to the “real” shutdown menu.

I’m not familiar with whatever technology this is, but I too would like the option to sleep or hibernate.

Figured it out.

Open the Power / Session tab:

Then right click an option, and add/remove as favorite:

I’m not too familiar with adjusting that menu.

But assuming it’s not a simple process you could add a script to your favourites there that does what you need.