There is no default font size for all dialogues - a dialogues font size is (if you're not using text codes for the font size) determined by the GUI box that is used to display it.
The GUI box defines the font size of dialogues in the Content Box Settings and for choices in the Choice Settings (and for the names in the Name Box Settings. Changing that font size in a GUI box will change it in all dialogues that use the GUI box.
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The GUI box defines the font size of dialogues in the Content Box Settings and for choices in the Choice Settings (and for the names in the Name Box Settings. Changing that font size in a GUI box will change it in all dialogues that use the GUI box.
If you're enjoying my products, updates and support, please consider supporting me on patreon.com!