Mylyn allows to you reveal what is inside of a folder by clicking on it while holding the 'Alt' key. For some reason it worked for me in Fedora as 'Fullscreen off'. Now I know why :-). The reason is this default KDE setting:
One rule that I always follow while creating key shortcuts is that 'Windows'/'Meta' key is used for application management purposes and interaction with the operating system, while all other key combinations (without 'Windows'/'Meta' key) serve for application purposes.
Changing the 'Modifier key' to 'Meta' restores Mylyn functionality and reduces the space of possible conflicts with other applications.
BTW. You can imagine my despair when Unity was introduced to Ubuntu and the 'Meta' key always activated it...