Truespeed, patience.
One thing that i've learned about open-source software (that could be applicable, more or less, to closed-source/traditional software):
1) "If you need a feature, suggest it and wait an answer"
2) "If you can't wait, code it and share it".
3) "If you can't code it, wait until someone code it".
4) "If you can't wait, shut up".
With FlashFXP i advise to follow point 1) and the second part of 3). At the end you'll probably see the feature implemented (like, for example, language translations
)