Is it permissible to use affectionate diminutives for names such as "Abd al-Rahman," "Abd al-Malik," and "Abd al-Samad," given that they are composite names incorporating attributes of Allah?

There is no harm in altering the first part of names like 'Abd al-Malik or 'Abd al-Samad for endearment; for instance, saying 'Ubayd al-Rahman, 'Ubayd al-Malik, 'Ubayd al-Samad. This is because the alteration pertains to the word "'Abd" (servant) and not to the name of Allah, عز وجل.