[NTG-context] additional footnote (quite late)

Hi, sometimes – just before the printer heats up his machine – there is something important too add, but yet the footnote-numbering can't be changed anymore (see example below please): \starttext First sentence.\footnote{First footnote} Something added\footnote[-]{In-between footnote}. Second sentence.\footnote{Second footnote} \stoptext Do you know a reliable way to make footnote "In-between footnote" labeled "1a" (in text and page end)? Steffen