When the strings of the harp are detuned for a scordatura, there are several things to consider:
Detuning a string affects all the notes on that string. For example if a c string is detuned, the c-sharp, c-natural and c- flat notes on that string will all be detuned.
Lowering the pitch of the string causes no problems.
The pitch of a string should not be raised more than a semitone. The strings already put great tension on the frame of the harp. Raising this tension can cause the string to break or even have a bad effect on the frame of the instrument itself.
Detuning the strings takes time. Retuning them also takes time. Furthermore it may take the harp some time to become used to a different tuning. This depends on the instrument and the quality of the strings.
Detuned notes should always be notated as they are played and not as they sound. It is possible to write the sounding pitch in small notes, but this is not necessary. Because of the pedals, harpists are used to the fact that a string does not always have the same pitch. Therefore, they are not likely to be confused by seeing a different pitch written in the score than the sounding one. On the other hand, it would be extremely confusing for a harpist to have to play a different string than the notated one.
The scordatura should, therefore, be noted in the legend of the piece or at the beginning of a passage. Then the music should be notated as played, taking into account that the scordatura affects all notes played on the detuned string.