It would really be helpful to add a mode which will echo keystrokes in one tab to all tabs in the same window. This broadcast mode would simplify repetitive tasks. Reproducible: Always
That feature has been available for a long time. Go to "Edit -> Copy Input To -> All Tabs in Current Window"
I thought surely someone had implemented this feature, but I couldn't find it. Thanks for showing me where it is, and sorry for the spurious bug report.