The other day, we received a review on the iTunes Store for Keyman, which was really a support request. Now the problem with asking for help in the iTunes reviews is that Apple provide no means for us to respond to you. This is unfortunate, especially when, as in this case, there is a simple answer to the problem!
Please continue writing reviews -- but if you have a question, just drop us an email to firstname.lastname@example.org as well!
This time, I'm writing an answer to Elias as a blog post, in the hope that Elias will stumble across this answer, or that at the very least, it helps other Amharic users of this keyboard layout. But this is clearly not the most efficient way to help you! :-)
The complexity of entering Amharic and other Geez script languages can be bewildering, and even the GFF keyboard layout, arguably the best yet devised, is limited by being designed around a standard "US English" physical keyboard using phonetic relationships between the Geez and Latin alphabet characters.
But help is available! The complete guide for entering the Geez characters can be seen by touching (i) on the Keyboard entry for Amharic. This will display a sub-menu indicating the keyboard version and a link to the complete Help documentation for using the keyboard.
To answer Elias's specific question: to enter the Geez character ሴ it is necessary to use the input sequence 'sie' (ስ ኢ እ on the keyboard), not just 'se'. As Amharic has many more vowel sounds than can be represented by the Latin alphabet vowel letters, some syllables require entry of more than one vowel letter. This is also the result of the keyboard having been translated from a desktop layout, as described above.