Dear Maija,
You are absolutely right, we have disabled the direct PDF coding (we call it "inductive coding") in the "coding only" interface. We decided this based on two considerations:
1. The inductive coding typical procedure involves creating new descriptive codes as one reads the PDFs, this won't work in the "coding only" interface because it does not allow to add or edit code-trees at all.
2. The Coding Only Role is designed to force people in the coding-only interface, we created it to allow people to go through an enforced round of blind double (or multiple) coding: in the full interface, people would be able to peek into each other's decisions. Doing a double blind coding round of inductive coding would not work: it's virtually guaranteed that each reviewer will code PDFs in slightly different ways, and EPPI-Reviewer would probably see only disagreements.
As a result, we decided that inductive coding should be disabled in the coding-only interface. For the time being, if you need to do some inductive coding you should ask the review owner to remove the coding only role from your account. However, we are always open to suggestions: if you have reasons to believe we should change this behaviour please do make your case, we we will be glad to think about it and discuss it further with you and/or your team.
I hope this clarifies,
Sergio