This plugin for OTRS (version 6 and newer) will allow your agents to add predefined labels to tickets. The administrator has to define all labels and define the queues which will be able to use those labels. There are already plugins available which bring the feature of ticket labels but the maintenance is too heavy.
This plugin is distributed under the AGPL3 license which allows everyone to use and modify the software but also invites to review the code or even contriubute new features and bugfixes to the source. In case you are interested you can just create a issue or fork the project and send me a merge/pull request.
- Marius Timmer