There is a certain window that I set to hide title bar when maximized.
Now it hides title bar even when not maximized, so I don't have anywhere to right-click and fix its settings.
What to do?

shmu26 wrote:... hides title bar... so I don't have anywhere to right-click and fix its settings.
What to do?

I don't know, but I recently learned that control-M toggles the menu-bar on and off for some things. Does that give you anything that lets you turn the title-bar on again?

robbrown wrote:

shmu26 wrote:... hides title bar... so I don't have anywhere to right-click and fix its settings.
What to do?

I don't know, but I recently learned that control-M toggles the menu-bar on and off for some things. Does that give you anything that lets you turn the title-bar on again?

I can't get that to work. I can't even unmaximize the window from the controls on the panel icon. It's corrupted. If I knew where to look for the file, or the line in the file, that controls this window, I would just delete it and let it default.

You can always use Alt+F3 to get the window menu that you normally get by right-clicking on the titlebar.
You can also get to the window rules and such from System Settings -> Window Management -> Window Rules.

This happened to me once.

I had actually installed a widget called Active Window Control and in that widget's settings, I had enabled an option called Hide title bar for a maximized window

Now I disabled it and it is working well and good(the title bar is not hiding)

This might be your case as well

I ran into this with newly installed Kubuntu 22.04 just recently.

For some reason some windows hid their titlebars (Chrome, Signal and Telegram Desktop to mention a few), and I couldn't find any way to unhide them.
I however found a setting in System Settings/Window Managment/Windows Rules/whateverapp, a property called "No titlebar and frame".
Added that property, chose Force and set it to "No", and hey presto - the close, maximize and minimize buttons showed up again!

I'm pretty sure there must be some global setting somewhere in System Settings, to control this, but I for one couldn't find it.
Unless the default with Kubuntu 22.04 is to hide the titlebar??