As described in T26485, current behavior when activating any segmentation tool is to overwrite the display interaction config with a hardcoded config that doesn't use the left mouse button (DisplayConfigMITKNoCrosshair.xml) and restore the original config when the tool is deactivated. This does not work when the PACS interaction is used, since it is still overwritten by the default config (without crosshair).
To solve this, I propose to switch from setting a new config in mitk::Tool::Activated() to adding it to the current config. This way one does not need to handle all the unchanged interactions, only the ones one wants to change. For example, for segmentation tools, instead of hardcoding the entire config, one can just add a config that only contains a non-functional interaction for the left mouse button. This will block any events of that kind to be handled by the original config, but won't interfer with any others.