When I insert new text (insert textbox) or when I type in a presenter note, the default font size is 18. Can I change the default to 24? (I know about master slides but since text boxes and presenter notes are not place holders...)
I found a solution posted on the Apple support forums. To set the default font size for new text boxes, create a text box, give it the font you want, then choose Format > Advanced > Define Text for All Masters.
There's a fairly complicated method of doing this posted here. I don't believe there's a supported, non-complicated way.
I know the simple but pretty primitive method. You click on text box and new text box appear on your slide. You create 10-20 new text boxes, select all and select the size you need. Now you ready for work :)