Flash Everywhere

Key Flash Everywhere in ExCfgShtFmtFlash refers to a boolean that controls which cells, out of those containing the Deriscope function, get flashed, i.e. have their color temporarily changed, as soon as their contents get modified.
Set TRUE for extending the flashing behavior to all cells of all worksheets and workbooks currently open.
FALSE for affecting only those cells that lie in the visible part of the currently active Excel window.
Obviously FALSE is the most efficient choice and also the only sensible when the flash duration is so short that the flashing of the non-visible cells would be a waste of resources.
TRUE makes sense during spreadsheet auditing, but it then needs to be accompanied with a sufficiently large flash duration as set in Flash Duration
Set Flash Duration = 0 to eliminate the flashing behaviour completely.