Let's make a text box and fill it with text. Then, select some text and, in the Options Bar, choose Split 2 to split a portion of the text box into two columns.
Question: How can we control the gutter width of these Split columns? (I have tried many things without success.)
If you're on a Mac, try Option clicking the icon to left of the Split/Span drop down menu. It took me quite some time to figure this problem out myself.
The dialog box for settings of Span and Split columns can also be accessed from the Flyout menu of the Control Panel (next to the Quick Apply button).
That is great! I never knew these options existed. And, these options can be built in to Paragraph Styles! (Adobe ought to publicize them more, or at least make a drop-down menu instead of the hidden option-click. No matter now that I know it is there.)