Something akin to how Swaywm and Alacritty behave. The user can set an option in the config file and run a command to reload iamb with the new settings without quitting and relaunching. Perhaps a :source or :source-config command.

If there's some error in the config, iamb provides :messages as to what those are and falls back to the previous config state.

Additonally, :edit-config or similar command could be used to invoke $EDITOR and persist the current iamb session. When the file is saved and closed, iamb reloads with the new config, barring any errors the user made.