Thank you for your answer! I also saw the instructions from the Smithsonian. That seems to be specific to their transcriptions, which are probably later edited by software (similar to our templates and categories), to become the final version - in print or online - where the actual strikethrough is added.
I am asking what one does if they do not have access to the actual strikethrough (as in our case in biographies).
Hope I have explained this adequately. Thank you!