How Can I Edit a vegetation .PgTcDx file?

I think I've figured out why one of my shrubs with a _wi entry won't show in winter, but I can only use RW_Tools to look at the .PgTcDx file's contents not make any changes.
The save changes button in RW_Tools is greyed out when I try to save a new entry.
So the question is, how do you guys edit the contents of those folders?
I should also add, that using RW_Tools I found nothing in that Embankment2_wi file but a white square for an image.
It all makes me wonder if I should try to set it up to use the _au texture in winter. At least the embankment bushes would look a little shriveled.
The save changes button in RW_Tools is greyed out when I try to save a new entry.
So the question is, how do you guys edit the contents of those folders?
I should also add, that using RW_Tools I found nothing in that Embankment2_wi file but a white square for an image.

It all makes me wonder if I should try to set it up to use the _au texture in winter. At least the embankment bushes would look a little shriveled.