No matter what I do, change date field font size or other layout settings on the field, the drop-down calendar icon size stays the same (small).
This doesn't look nice with a large font size date field.
If you turn off the option "Include icon to show and hide calendar", then the calendar is activated by entering the field.
Therefore you can make your own button and set the icon to any size you want. Set that button to go to your field.
Only color can be changed for the icon... unbelievable...
I didn't want the actual date field to be editable. I wanted the popup calendar to be the only way to set the date of a "display only" field.
But with using your idea and setting the editable date field behind with font size 1 and 1x1 dimension, I got what I wanted.
Not perfect because even being behind the button and with the font size 1 and 1x1 dimension the "text insertion point" still shows. But acceptable for now.
If you are using FileMaker 16, you could look at using this Card Window date picker tool
Card window - date picker
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