How can I remove this space?
According to this GitHub issue:
This difference is due to a bug Powerlevel9k that is too severe to emulate in Powerlevel10k.
If you want your right prompt to be at the edge of the screen without indentation, add
~/.zshrcand restart zsh. The default value of this parameter is
1, hence the space you are seeing. This parameter is respected by all prompts except Powerlevel9k.