window_scenery_tab_entries located in libopenrct2ui/windows/Scenery.cpp is an array of all of the scenery items on a tab in the scenery window. The type is uint16_t but this is actually a lie. The type is actually a struct of scenery type and scenery tab index stuffed into a uint16_t! This issue is for fixing this.

Create a new struct for the tab entry that has two fields type and index. Modify all of the code in this file to use the new struct for the type of window_scenery_tab_entries. Try to make the changes in stages. Its easy to convert between the old version and the new version as its just a case of stuffing it back into a uint16_t.