Is there a way to scale up a bunch of rectangles in the x or y direction by the same delta value?

Hi @TestriteVisual , I think you would have to use a script. try this:

app.scriptPreferences.measurementUnit = MeasurementUnits.INCHES;
var h = 5;
var s = app.activeDocument.selection
var b;
for (var i = 0; i < s.length; i++){
    if (s[i].constructor.name == "Rectangle") {
        b= s[i].geometricBounds
        s[i].geometricBounds = [b[0],b[1],b[0]+h, b[3]]
    } 
};   
app.scriptPreferences.measurementUnit = AutoEnum.AUTO_VALUE;