It would be great if the user can select which vector objects in a layer are displayed at a specified cut-off scale.
In the Layer Properties> General tab> Scale Range Section, you can specify the range of scales at which the layer will be displayed; either "Show layer at all scales", or "Dont show layer when zoomed at specified minimum and maximum scales.
This could be improved by adding another option button for
"display only the objects with a specified tag field (listbox from which a user can select a tag field) and tag value (listbox from which a user can select the value from the field)
when displaying beyond the pre-defined scale cutoff or when zooming to extents.
This display limitation should be disregarded when zooming in beyond a threshold level to show all objects in the layer.
Similar to limiting the range of scales when a layer can be displayed, but also extends to different classes (as defined in a tag field) in the same layer.
For example, you have a shapefile composed of major topographic contours as well as minor contours and a field in the table with the fieldname "tag" with values of "major" for major contours and "minor" for minor contours.
This tag field can be used to display only selected classes but should also be usable to select which
classes will be displayed when zoomed out (to extents).
With the proposed improvement, only the objects with the specified value in the tag field will be displayed when the scale is beyond the cut-off, up to zoom extents or zoom all.
(E.g. only major contours are shown beyond the cut-off, otherwise show all objects in the layer).