The text in the note cards and scripts is not considered an UI-text and is therefore not affected by the UI size setting.
The note-card font is not really small... As for the script editor, it is indeed small (so to be able to see enough code in the script windows).
There is no runtime setting for it, but you can nevertheless change the script editor font size by editing manually the skins/default/xui/en-us/fonts.xml file.
At the end of the file, you will find that block:
Simply replace "9.0" with a larger number such as "10.0", "10.5" or "11.0" (at 11.0 and above, the risk is to see the line numbers "bleeding" into the script text area).
You could as well change the Monospace font for another, larger one (that has to be part of your system). To do this, edit this block:
and change profontwindows.ttf for another.
Be aware however that this file will be overwritten at each new update of the viewer (so just keep a copy of your custom file to restore it after updates).