Do you know about the build log tab?
Yes. It's as I've come to expect and want from dozens of IDEs - the raw log from which a table of parsed messages is generated. Perhaps I'm missing something though - does it help?
In the meantime I've stumbled upon a bit of a workaround - if all the columns are "big enough", giving just enough to the File and Line columns and more than enough to the Message column, such that the total width of the columns is more than can fit in the window, a horizontal scroll bar appears. The scroll bar can be positioned to only show the "most important" part of the path is visible. Importantly, this scroll position appears to stick between builds and selections. This is not the method I was expecting, but ends up really close to what I was after.