I have a QGIS project that includes a grid decoration. Is it possible to display this decoration only when zoomed in? I.e. can decorations in QGIS have scale dependent visibility?
Yes, you can use the Datadefined override of the symbol which you use for your decoration. Open the symbol properties, then go to the line symbol and overide the color with this expression. It will make the line transparent if the scale will be less then 1:50.000 else it will be red:
if( @map_scale > 50000, color_rgba( 255,0,0,0),color_rgba( 255,0,0,100))