The beam tool will beam or unbeam selected notes. This of course only applies to beamable notes, which are the 8th and smaller values that would otherwise carry a flag. You can't beam quarter notes - but beams for smaller values can be useful in showing where beat divisions lie. In general music is easier to read if values smaller than a quarternote are grouped by beams to mark the beat divisions, as in this example of eight 16th notes in 4/4 time:
One of the options in the lyric info window (available by clicking the info button at the left of the lyric line control) is the option to use vocal beaming - where instead of showing the beat, the beam indicates which notes are on the same syllable, as if there was a slur.