Install Python 3. Then:

pip install deftree

python resize_font.py <path_to_project_root> <name_of_font> <amount_to_scale>

This will look through all .gui files for text nodes with font <name_of_font> and scale them by <amount_to_scale>.

This doesn't support game object labels. Feel free to submit a PR

python resize_gui.py <path_to_project_root> <amount_to_scale>

This will look through all .gui files and scale all measurements (position, size, slice9) by <amount_to_scale>. Use this after you changed your project's design resolution and after you re-exported all the assets at the new resolution.