Read here: Console commands changes after V0.148.6 and forward
In this version, we changed from imacheater to devcommands to show what they are ment for. They aren't ment to be used by people to "test things" by normal users.
The issues are many:
Bricked worlds are one of the worst (spawning things)
Characters broken after spawning a monster weapon by accident
To access the console window:
* Before starting Valheim, go to your steam library, right-click on valheim and choose "properties", then write -console in launch options.
* This will allow you to open the console window via f5 in game.
* Use the new command: "devcommands" and you will get prompted by a warning message.