1. Compositions which have missing addons need to be handled differently. I suggestion to gray them out in the tree view or hide them.
Right now, if one selects a composition which used an object from a missing addon, a popup message is shown, which can become frustrating if one has a large number of compositions.
2. The combo box (configfile >> "Display3DENSaveComposition" >> "ControlsBackground" >> "Content" >> "Controls" >> "Category") should be replaced by a list box with a search functionality. The list of available categories is quite large and a combo box is not ideal for this. Same applies to the combo box (configfile >> "Display3DENEditComposition" >> "ControlsBackground" >> "Content" >> "Controls" >> "Category")