Published v1.73 running on Mojave 10.14.6
To reproduce:
1. Create master spread, facing pages, one text frame per page (flow linked) with 3 columns.
2. Create two pages.
3. Preferences -> Keyboard Shortcuts -> Publisher -> Text -> Insert -> Breaks -> Column Break
4. Set short cut to Shift + Opt + Return
5. Note -> shortcut now appears correctly in the Text/Insert/Breaks/Column Break menu item.
6. Edit text on the first page, begin entering text
7. Press the short cut defined above and enter more text
Expected: cursor to move to 2nd column and new text to appear there. If "Show Special Characters" is enabled, a curve (like a closing round bracket) symbol at the end of the last line in column 1.
Actual: cursor moves to next line on first column. With "Show Special Characters" enabled, a line break symbol is shown where the break was inserted.
Additional:
Similar incorrect behaviour when using the enter key instead of the return key. Shortcut appears correctly, behaviour is wrong. Appears to work ok with keys other than enter/return. But think of the design intent - hitting return adds a break; it makes sense that hitting return with a modifier would be able to create different types of break.