Q. (Re- question 2201 above). When is Muktza more severe on Yom Tov than Shabbos? And is not Muktza only a Rabbinical prohibition, so how can you comply with Tosefes (adding to Yom Tov) which is a Biblical mitzva by accepting Rabbinical melochos?
A. Shulchan Aruch (O.H. 495: 4) writes that Muktza items that are permitted on Shabbos, our Sages were stringent and forbid them on Yom Tov. Mishna Berura (15) explains that it refers to some types of Muktza permitted during Shabbos, such as items that were stored for an extended time, or dedicated for sale, or are disgusting and offensive. On them and others, our Sages were lenient, since people, due to the seriousness of the Shabbos kedusha and holiness and the severe gravity of it’s prohibitions, are careful not to violate them. Thus, they will not proceed to become careless and negligent. That may not be the case during Yom Tov, when many melochos are permitted for Ochel Nefesh and food preparation. If we were to further be lenient in Muktza, they may come to desecrate Yom Tov.
The fact that Muktza is only Rabbinical, does not mean that it cannot be part of a Biblical Tosefes Yom Tov, since after all the Torah instructed us to listen and follow the mitzvos given by our Sages.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a