I ended up doing a dirty hack for the time being, but I hope to sit down and adapt it properly at some point. 
Code: ags
Hacky, but it works for now.

function checkGUI() {
if (GUI.GetAtScreenXY(mouse.x, mouse.y)) {
hoverOver = GUI.GetAtScreenXY(mouse.x, mouse.y);
if ((hoverOver == gExplorer)) {
DragDrop.AutoTrackHookKey = true;
}
else if ((hoverOver == gDetails)) {
DragDrop.AutoTrackHookKey = true;
}
else if ((hoverOver == gResume)) {
DragDrop.AutoTrackHookKey = true;
}
else if ((hoverOver == gConfirmation)) {
DragDrop.AutoTrackHookKey = true;
}
else if ((hoverOver == gDropdown)) {
DragDrop.AutoTrackHookKey = false;
}
else if ((hoverOver == gMainMenu)) {
DragDrop.AutoTrackHookKey = false;
}
}
else {
hoverOver = null;
DragDrop.AutoTrackHookKey = false;
}
}
Hacky, but it works for now.