The Trial version won’t create fonts including accented characters — it just outputs a subset of characters.
See the FAQ at the top of the support forum.
Obviously, there is no problem with producing fonts with accents. FontCreator is also compatible with Windows 8
How you type the characters that you need to use is not the job of FontCreator. I use a customised Windows keyboard to type all manner of accents required for Pāli: ā ī ū ḍ ṭ ḷ ṃ ṅ ñ ś etc., but you need the registered version to produce fonts with characters in the Latin Extended character sets.
The Professional Edition makes the creation of accented glyphs semi-automatic using the Complete Composites feature.