I use LLD quite a lot, for instance to detect physical disks on Linux hosts to get disk i/o stats.

With LLD it is possible to define graph prototypes, so that for each detected item, corresponding graphs are created. It is however not possible to define a graph in which multiple such items are combined.
For instance in the case of disk i/o, I would like to stack i/o-stats from all detected disks in one graph, to see total combined disk i/o.

Another example is temperature sensors. There can be many such items, since most modern motherboards and processors have multiple sensors, and most hard disks also have one or two sensors each. It makes little sense to have 24 temperature graphs for one host, I want one graph containing all temperature items. Again, this is not possible with current Template/LLD configuration.