I was just trying to figure out how to do this on my iPad Pro. I was shocked to discover that this isn't already a basic feature. For me, project-wide text search is what separates an IDE from a mere editor. Even Coda for iOS doesn't support this yet. Please make this a priority. It's the difference between using iOS for casual edits or serious work

For anyone looking for SASS support, Alexander (the developer) responded to a question I posted on Facebook. Not only is SASS support planned, but it's possible to add support immediately following these directions..

"I'm going to add support for it in an update. For now, you can install a TextMate bundle like this one: https://github.com/alexsancho/SASS.tmbundle - it's explained in the manual:http://www.textasticapp.com/mac/manual/lessons/How_can_I_add_my_own_syntax_definitions__themes_and_templates.html"

SASS/SCSS is absolutely critical for me and my team these days. Textastic desperately needs SCSS support.

It's particularly a problem when using Textastic to edit MVC-based web applications, since there are a frequently empty/undeveloped view files early on in a given project.