In the above, @currentField is used to extract the value of the current field/column.
And I see from here that it's also possible to use @currentWeb get the main site dynamically rather than hardcode it.
What I really need is something similar to get the folder for the current item, so that I can for example then refer to a sub-folder relative to the current folder, rather than relative to the top level, i.e. something like @currentFolder in the below:
And I can't see that using an actual Hyperlink type of column would work for this, because the full path name would need to be used... because it's just a string that is interpreted as a URL? I'd really like the ability to create hyperlinks that are relative to the current folder.