We have just added this as a feature (as of version 2.3.23) . To enable the marker to appear, you will need to add this line to your ptxprint-mods.tex file:
\def\marginversemarker{*}
where * is whatever marker you want to use. Note that you can also add a kerning space after the marker if required. So, for example, if you want a dash ‘-’ to be the marker to show where the verse starts and then have a 1pt space before the 1st word of the next verse, then use this:
\def\marginversemarker{-\kern 1pt}
Currently this does it everywhere (even at the start of a paragraph/line) which may not be ideal, but it is as far as we’ve got so far.
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Note that to change the size, color or styling (including raising or lowering the mark), you can change the \zmvm marker as shown here:
This ends up looking like this: