So you have two categorical attributes, one with 3 (edge type) another with 2
> What I would like is to preserve the visual intensity of ties while
> adjusting the colours of the ties.
You can map different visual variables. E.g. color <- edge type,
thickness <- backbone.
> My ad hoc solution would be to export the tie attributes, combine backbone
> and tie type in a new column, then reimporting and manually setting the
> colours for each of the 6 categories.
Which would allow you to map different colors to the same edge type (with
different backbone). Not so sure if that is a good idea.
That said you can construct the tuples in the attribute manager:
1. `manipulate > merge to list`
2. `manipulate > convert list values > concatenate`
Then map the concatenation with e.g. color table.