Hi,
using Simon with an OS X account that has french as main language, some 'buttons' are absent, e.g. Options and Notifiers 'buttons' when editing a test. (see attached Simon 002.png)
As a test, without logging off, I quit Simon, remove the Contents/Resources/fr.lproj and restart Simon, all 'buttons' appear (in english, of course). (see attached Simon 001.png)
It seems Contents/Resources/fr.lproj/TestEditor.nib is the culprit.
Having switched to english, I did no further tests in french, so it may be that other 'buttons' are missing.

Pascal;
PS: Simon 4.2, OS X 10.11.4 FWIW.