Problem: For many nodes, ports are labelled with numbers only. For nodes like Render Layers to Image, Render Layers to Window, these are currently labelled with numbers only. For others, there are no labels are all. The result that it's easy to forget which is which, without tracing the cables back through the composition. Real-time thumbnails may help, but will not help for numeric values, or when composition is not running.
Request: Right click on a port to rename, or add a name to a port. Easier version is to do this for ports that are currently labelled with numbers.
for example, these labels might be 'cow' 'moon' and 'starry background' for images. Or 'motion index' or 'mouse movement vector'. These are, in essence, variable names.
Bonus points: Allow labelling to cascade through an entire flow.