The screen files are not in the pervasive ddfs in the screens folder, but dgillz & I had someone modify the existing ddfs. However, the data from those files doesn't come in clean. You can, however see which users have which screens. I didn't try the union syntax thing that dgillz suggested to link all the btr files together, but I was under the impression the union syntax didn't work in pervasive. If you want to experiment, we can get you the necessary tools. I don't know that I would try to update those screen files for individual users since we weren't able to get completely readable ddfs. I had also hoped that I could delete screensets for non-existent users, but had no success with that.
Also unclear here is changing user screensets rather than groups. You can apply the screensets to the group level. In OE, for example, I use a user defined field with a drop down list of users who enter orders. Then I give the screenset to the entire group since they choose their user ID during order entry, then it writes to the file directly. No need to modify everyone's screenset. I find it much easier to administer the group level, especially when there are many users at a particular site.