To expand on @Jörg Vogel's answer, to include a label automatically as part of a newly-dragged-from-the-library object, you need to edit its definition in the library. However, as he mentions, this will not persist once FlexSim is closed - you will need to edit the library object again each time you open FlexSim.
One alternative is to create your own Custom User Library of pre-labeled objects. Your library can load automatically when FlexSim starts, and you can drag items from your own library just the same as if from the default library. The benefit of using your own Custom User Library in this way is that it can persist across FlexSim instances.
Using that same Global Preferences Libraries interface, you could even choose to show your Custom Library and hide the defaults.
