Fast user switching, perhaps? You could probably create the new account, note the user/group of the new account, then copy the contents of your main account ho

Fast user switching, perhaps? You could probably create the new account, note the user/group of the new account, then copy the contents of your main account home directory into the new user's home directory. Then chown -R as appropriate so that the copied files belong to the new account. That ought to give you a second user account, that has an identical environment to the one you've been using. You might want to use different desktop images so you quickly know which account is active.