Extension line in figured bass notation

[Tim Yang]

In figured bass notation currently we can use \bassFigureExtendersOn
to represent repeated chords. However, In many baroque music scores I
encountered, often there are lines
drawn without a figure preceding it.  I believe this means the root
chord <5 3> is held,
because this chord is omitted as default.  However, currently it seems
there is no way
 to draw a line without a figure preceding it.  Also, according to the
explanation I found for such extention line, it means a chord is held.
Holding a chord and repeating it seems to be different concepts.  Also
in many places, when extension lines are drawn, I see a single line,
not seperate lines drawn after each stacked figures.

Maybe there should be a way to simply express a "extension line"
rather than writing repeated figures, or is there a way to draw such
line right now?

Tim Yang