I prefer to use maximized windows while working.

When Krdc connects RDP host, window exits maximized state (become normal) and after logout from all the opened connections, KRdc window becomes maximized again.

Maybe this helps:
Right click at the window decoration -> Advanced -> Special Window Settings -> Maximized horizontally/vertically

(Maybe the words are a little bit different, but this should be the path)

Use "Force" as setting and check the checkboxes for both.

JanGerrit wrote:Use "Force" as setting and check the checkboxes for both.

I am using "Force". That is why on logout my krdc became maximized back.

Ah, ok.
I don't know, maybe it's a bug in KRDC?

Note that KRDC may be creating a different type of window when it makes the actual RDP connection.