Did you ever think, it would be handy to multi-select all DataCardValues & DataCardKeys in a Form at once?
I accidentally found an easy hack to make this happen:
1. Select the form
2. Change Layout from Horizontal to Vertical (or vice versa)
3. Hit once the Undo icon.
This makes all DataCardValues and DataCardKeys beeing selected. Now you can easily mass change the available propertys, e.g. link fontsize to first DataCard in your form or do whatever you need. It does not work for all type of controls (e.g. dropdowns) but at least for textinput & their label.
You can even deselect the ones you don't want to be selected using the CTRL-Key while clicking. (e.g. select only keys, only values)
btw: the undo trick might help you as well after having resized the App Screen size (which resizes all controls in the app proportionally) to make the controls having the sizing as before the screen resize...