This actually comes in two parts.
1.- eM Client 5.0 now persists the currently selected mail in the folder lists within the same mail session. Can you extend this to store it between mail sessions? i.e. select a mail in a folder, close eM Client, open eM Client, go to the same folder and the same mail is still selected.
2.- Persist the currently selected folder in the action dialogs, for example Move/Copy to a folder, move a rule up/down, etc.