Problem:
In Mouse preferences, the list of bindings has a dummy empty column, which is a workaround for getting the Tool column to be right aligned. As a result, Narrator reads the list as having 5 columns which is confusing. In addtion, when arrowing down such a list, Narrator initially just reads the contents of the first column, which is unfortunately an empty string.
Fix:
After all the columns have been inserted, the dummy column can be deleted. This workaround was suggested by some Microsoft documentation.