Romford - Upminster does exist as a graph.
Only question is why? If you can’t timetable that then no graph is going to save you. But I guess if you are training folks it’s a good introduction to the principles involved.

You still need a Mk1 eyeball in most cases.As an outsider I would have thought, when trying to fit in an extra path on a single track route (with passing loops), that looking at a graph is easier than looking at a timetable bank. Far easier to spot the potentials / problems? As they say, a picture paints a thousand words.
Go on, tell me that modern software does it in a microsecond!
You still need a Mk1 eyeball in most cases.
Or if you have a few hours, try Switzerland:Figure 2 in this link gives you some idea.
http://www.railway-technical.com/operations/working-timetable.html
Or if you have a few hours, try Switzerland:
https://www.fahrplanfelder.ch/en/archives/train-graphs.html
(the English label is slightly misleading, it's routes not individual trains).
The default of train planning seems to be moving towards editing a timetable via a graphical interface. Personally I’m not a fan, my mind works in tables and headways, not visual lines. Not very easy to plan complex station workings purely on a graph either, the bar-chart approach is unbeatable imo.
There are and it depends how you were taught to some extent. I prefer graphs but could do tables and TRUST but find those less natural.
The default of train planning seems to be moving towards editing a timetable via a graphical interface. Personally I’m not a fan, my mind works in tables and headways, not visual lines. Not very easy to plan complex station workings purely on a graph either, the bar-chart approach is unbeatable imo.
There are definitely "graph" planners and "table" planners!
Blobby is still around but alas no longer does platforming.