Ability to add a glissando to an unique note
It's often done on violin notation to put a glissando on an unique note like in this file, a glissando line with the word glissando or with a waved line like in this file. MuseScore only allows this type of lines between two notes.
Workaround : Use two voices. See steps (in french) in this file.
Full discussion (in french): http://musescore.org/fr/node/7611