Okular with an additional annotation tool
The motivation for this is interoperation with downstream applications. Those often read the content of annotations but not highlighted text. On default, Okular highlights text, but leaves the annotation empty.
This topic was discussed in kde-bugsand superuser. In response, a small modification was suggested by jsqlio. The suggested modifications are put in practice here. But instead of changing the default highlighter behaviour, a new parameter (key) is introduced. Only if key is checked, the selected text is copied into a note. Furthermore, a key text can be specified, wrapping the selected text xml-style ("selected text") in the note. With this, the highlights can be classified and the text easily filtered by a downstream application.
This leaves the choice what to do to the user. One can distinguish highlighted ares which will be imported into Docear (key checked, blank text) and ones which are not (key not checked). If applicable, downstream filtering can be achieved by having key checked and an additional text.
This repository was cloned from the kde git repo with modifications in the respective branch. For building, please see the Dockerfile included in the repository. It sets up an Ubuntu build environment for Okular. Follow the instructions in the Dockerfile itself.
No guarantees whatsoever are given. The software is highly experimental and hardly tested. Use at your own risk.