Everything can be placed and remembered, but does not survive through modification. I.e., if you change anything, then all the placement of items connecting to it will get forgotten. E.g., if you change a node's text, then all edges that connected to it will be automatically re-placed, and so are the the texts that associated with the edges.
Hence, if you don't like where tcm place things, it will be a nightmare to maintain the diagram. Further, the tcm is really not good at placing things, e.g., the edge text are placed over the edge, which 99% of time looks bad.
Nuisance:
Nuisance: