L'istesso Tempo

Is it possible to have a L'istesso Tempo when changing time signatures. It doesn't necessarily need to be included in playback, but I find it helpful when reading notes to have one. It would be something like:
[dotted crotchet = l'istesso crotchet], only in actual notes, not text, appearing above the time signature change. Does this already exist? If so, how would I do this? If not, could it be added to a future version? I guess adding it as a symbol would be the most practical... Thanks