Is your feature request related to a problem? Please describe it.
Currently, \input{a_b.tex} highlights the a_b.tex in light blue color. However, \import{directory}{a_b.tex} will highlight the _ as an error.

The \import command is provided by \usepackage{import}.

Describe the solution you'd like
The _ is not highlighted as an error, because it is part of a file path.

Similarly for \subimport.

Additional context

See package description: http://www.ctan.org/pkg/import