The opening text in the gif reads:
I'm INSERTING EMPTY TIME - Doubling the number of 7/4 bars. Why does it add 4/4 bars? And what's with the extra tempo marker
Actually... that extra tempo marker added at bar 17 is also a 2/4 bar.
It seems to me that Reaper should just add 7/4 bars?
Here's how to replicate:
Pick a bar
Add a time signature. I chose not to add tempo, just the time sig... in this case 7/4
Pick another later bar
Add another time signature as before, reverting back to 4/4. (no tempo)
Make a Time Selection of the 7/4 bars
Use "Time selection: Insert empty space at time selection (moving later items)"
Viola!
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I understand why this behaviour would be desired. After all, if I were adding 4/4 bars to the end of the 4/4 section, how else would I do it?