I understand that many hold it is permisable to use the adhesive straps on pamper type diapers on Shabbos so long as their use is temporary. Would this also be the case for using "post-it" note as a bookmark as one is reading a Sefer?

The reason the nappies can be used by these authorities is since the sticky straps are only temporarily attached. The post-it-note can stay for a longer period and therefore shouldn't be used. (Shmirat Shabbat Kehilchata 15, (250)