Difficult to say. From the question, it appears that the most appropriate way to tag it is contingent on the answer to the question itself: Based on Is this a manner of praying/supplication
, either salat or dua would make perfect sense, but you obviously can't know which until after the question is answered. Tagging with both "just in case" could potentially confuse the issue more.
islamic-basis is a good fit; it easily falls under the definition of "Questions seeking to understand what, if any, Islamic basis a commonly-held practice or tradition actually has can be asked under this tag," even if it's clearly an Islamic practice (rather than Folk Islam)
Beyond that, we would probably be better off if we had a tag encapsulating "Activities concomitant with salat but not actually part of the salat itself", but I'm honestly at a loss as to what to call it.