In Lichess, any form of external help (e.g. engines) is forbidden, even in correspondence chess. However, there is an option to open a separate board where one can make unlimited scratch moves.
I would regard using a separate board as cheating because building variations in the player's mind is in the spirit of chess and is subject to failures. For example, overlooking a piece that refutes an attack could be eliminated by using a separate board, so while using it will undoubtedly hinder a player's personal improvement, not using it will place him in disadvantage over another player who does.
Assuming external help is forbidden, is it ethical to use a scratch board in correspondence chess? Am I wrong that it goes against the spirit of chess?