[SM-PLUGINS] switch for html mail / plain text compose?

[Bob C. <bo...@bo...>]

Is there any way to switch between html mail and plain text at the compose
screen rather than going to options->display prefs and making the change
for each email?  While I have set the default to html mail so that I can
reply to html using html, I would like to use plain text when possible
(like on this mailing list).  Is there an easy way to do this that I don't
see using SM 1.4.3a?  If there isn't a way currently to do this, is there
anything that would make it harder than I would expect to add it myself
(considering beginner level php skills)?

Thanks,
Bob C