Sorry, I could have been more specific. Rob was correct that the song was written in 3/4, and 4 bars of 3/4 should become one bar of 12/8. (This is something I have found happens often when doing string arrangements for pop tunes, but usually I do the transcription as well, and just convert on the fly)
Thanks for the thought about doing the insert mode. That mostly would have done the trick (although, been really time consuming, for a 9 minute track…), however, there were some 4/4 bars that were correctly labeled, that would have become problematic, as those time signature changes don’t move with the insert mode (as far as I know).
I think just a way to proportionally change the duration of a region of music would be the best way to resolve this kind of issue, as Dorico will be good about re-doing the bar lines. (This is a common feature in other scoring and sequencing programs, so I imagine it will appear here at some time.)