Tab spacing/ columns in graph legend

I would like to have two columns in my legend, because the traces fall neatly into two categories and I'd like a landscape rather than portrait legend. I can do this for one size of graph by just inserting tabs into the text box, but when I maximise the window, the spacing changes. I can change the tab width in the modify legend dialog, but then when unmaximising the window, the spacing becomes too large.

How can I achieve what I'm after (which is to maintain even spacing, with the RHS traces lined up in a column, when resizing the window)?
You need to use a fixed font size in your legend. You can do this by adding the \Z## code before the text that contains tab characters where ## is a font size in points.
Thanks - that does indeed work, but the font size ends up too big/ small on one or other of the window sizes. What I need is the tab size to be scaled along with the font size, when using relative font size. I guess this isn't possible? One for the wish list? I mean I could just have an external legend and do it portrait, but it's a non-ideal work around. Or indeed I could change it each time I resize the graph for exporting.