The Glissando tool is found within the Articulations section of the Symbols Selection window. It’s identified as a diagonal line between two notes.
Once selected and a note is clicked on, it will appear between that note and the following note. The effect will be a run of intermediate notes between the two without affecting the timing of either note.
Inserting and deleting a glissando mark
NOTE …
Glissandos are not editable using the Properties tool.