Unable to edit .strings file, shows up as greyed out?!

Binary files are greyed out. You can tap on it anyway and try to open it, but if it is not a proper text file, it probably won't open.

Any plans to add this functionality in the future?

.strings files usually have localization in them and it would be nice to be able to open them.

Did you try to tap on it? What happened?

Which encoding does the file have? .strings file are often UTF-16 files. Maybe your file doesn't have a proper Byte Order Mark (BOM). You could try to tap-and-hold the file, choose "Open with Encoding" and select UTF-16. Does that work?

Trying to open the file in UTF-16 crashed Textastic. Tried UTF-8 and UTF-32 and i see some text and stuff. Some of it readable.

First line says bplist00ß\

TextWrangler on the mac opens the file just fine.

I see. Your file is not a text file, but a binary plist file. You need to convert it to XML format to be able to edit it in a text editor like Textastic. You can do that on the command line on your Mac:

plutil -convert xml1 yourfile.strings

I would recommend renaming it to yourfile.plist afterwards in order to get proper syntax highlighting.

Any plans to add this in the future? I would like to have this kinds of files open natively on Textastic.

No, sorry, I think editing binary files is out of the scope of a text editor.