Add global level or book level text variables.
It would be nice to have book level text variable(s) that is used in documents in that book.
Richard Tyson commented
InDesign's Display Performance should be set to Typical. Watching high-resolution images causes InDesign to redraw areas so frequently that it uses up a lot of your processor's resources. https://domyonlineexam.com/
Josh Steves commented
YES! Running header variables dont work in textframes across spreads. This seems like a huge oversight. A global variable would fix this.