Hi Rudolf,

Sorry, but I can only answer in English!

LucasChess is a bit different to the other GUIs. You need to be in the Setup Position screen for it to accept a new position from lifting both kings. For example "Play > Play against an engine > [Initial moves] tab > Start position > Change". You can then enable the board in the top right corner, lift both kings and setup the new position. It then returns to the Initial moves tab with that position set as the starting position.

Hope that helps!

Graham