You must have created a DataTypeGroup.
1. Click on the DataTypeGroup datatype to open the "Datatype details" popup.
2. In the opened popup select the "Visualizers" tab and after that press on the "Parameter Space Exploration".
3. In the opened visualizer press on a datatype (in the middle of a colored circle). This action will open the "Datatype details" popup.
4. In the opened popup press the "Save" button.
Should close the "Datatype details" popup and save the changed data. I also expect to remain in the same viewer.
I'm redirected to a page from where I can select the DataTypeGroup for the "Parameter Space Exploration" viewer. This page will also display the following error message "launch() takes at least 2 arguments (1 given)".
The same thing happens for "Make relevant" and "Remove" buttons.