If I choose “Properties” from the “Project” menu, then select “Plugins” under “Open AT Application”, I see a list of all installed plugins, with a tick indicating those currently used by the project. For some plugins, there are multiple entries for the different versions installed. In my project, I am currently using WIP 5.1 but also have WIP 5.3 installed. Therefore 5.1 is ticked, 5.3 is not.
If I decide that I want to build the project with 5.3 and click on the check box for this version, a tick appears in the box for that entry, and 5.1 is automatically unticked. However, despite what the UI indicates, the plugin has not actually been deselected! If I apply the changes, close the dialogue, then open it again, I see that both 5.1 and 5.3 are ticked!
Even though two versions of the same library have been selected, the project will still compile without error.