Combining fields in an order table

Morning all, first time posting but hoping for some help.

I have a data source which has some fields in it, for the purpose of this lets call them field a, field b, field c and field d.

Now I want to put those fields into a different order, so I have created a table in my power bi document which links to the original table and changes the order. I have done this by having 3 columns, one order column (1-4), a column to match my source data (which I have linked with a relationship to my source table) and then a final column of the order I want - which correlates to the 'order' column.

Hopefully that makes sense so far?

Now the hurdle I have hit is that in some of my tables I want to combine the numbers in two fields (lets say field a and field b) but also show one field (field b) in a row by itself too.

So my main question is how do I do this? Example below of what it looks like currently.