The button 'Function' in the customization dialog has no function. If this feature is planned for later it would be good to disable the control.
You are right, and it is already disabled/hidden with this patch (waits to be merged): https://gerrit.libreoffice.org/#/c/41671/
You may observe the updated behaviour/appearance in the test binary presented in the final submission report: https://drive.google.com/open?id=0B-JvlLHm1-kKcW5xbmR5Q1l3bDg
Fixed with commit aad3e6d02eb65bccc720fdd1f10f60471e138906