luceos Thanks for replying.
I just translated many extensions (over 50) to my language (Persian) so people with Persian language could use my forum with our own language.
After Flarum 1.5 released, linguist doesn't work fine and i want to create a custom language. I only want to replace English lines with my translation.
linguist extension exported all of my translation with "YAML" format that included all of translated strings, So how can i use this without "linguist" needed?