When I wrote my initial post I did not try using tools button.
I just tried it right now.
I have tried to use the tools button at two places:
1. during the input select menu (after pressing input select button on remote)
2. when tv image is shown (no menu, just displayed what is received by the currently selected input)
At 2., I cannot see an option to change input names.
At 1., I am able to change the name of the input to some fixed pre-defined string (like "TV", "AV-Receiver", "PVR STB", "HD DVD"...) but I am not able to enter any user-defined string (e.g. I'd like to create the following individual names: "DVB-T STB" for AV1, "PLAY STB" for HDMI2 (Media Player) and "DVD HDD PVR" for Component input (Panasonic DMR-EH52).
Any further idea?