Adding tuplet marks

I imported a pdf to Musescore 4 using the new feature. It did not import the title, or the swing annotation. More importantly, while it imported nearly all the triplet notations, it did not import the sextuplet notations. It also did not import the grace notes, but I know how to take care of that. I don't want to add sextuplets; I just want to label existing notes as sextuplets. How do I do that? Naturally, omitting the sextuplet markings caused the program to misread some intervals, but I am hoping that will be cleared up when I add the sextuplet markings.