Topic moved to “Adding Features”.
Currently it is possible to “snap to” any of the available time units, but there are no time units for Bars/beats. (http://manual.audacityteam.org/o/man/selection_toolbar.html#snap)
There is also a weak “magnetic” effect when selecting to the edge of a clip boundary, or to a label position: http://manual.audacityteam.org/o/man/boundary_snap_guides.html
I wrote a plug-in that can generate labels (http://manual.audacityteam.org/o/man/label_tracks.html) at bar and beat positions. While this is not a full replacement for bars and beats as time units, it can be useful as a guide. The plug-in is available here: https://forum.audacityteam.org/t/beat-per-minute-labels/20785/1 If you find it useful or have any questions regarding it, please comment in that topic.
Audacity has a primitive “beat detection” effect that creates labels: http://manual.audacityteam.org/o/man/beat_finder.html
Unfortunately it does not work very well. “Improved beat detection” could probably be counted as a feature request vote if that is what you want.