I don't think that's currently possible.
You might try adding it as an option in the lw->pict function (or
something it calls). Beware, tho, that an ellipsis can have anything
at all inside it, so some care will have to be taken to get it to look
reasonable (I think it doesn't have to look great if the stuff inside
is sufficiently strange, but it should probably at least look
That is, this seems like something that'd be a reasonable option to
have for configuring Redex's typesetting setup.
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