I always felt there should be a quick select icon next to the file name (above the segments' iDs). Quite often selecting the segments gets annoying for large files where the focus is lost and you have to select the segments with your mouse and then use the keyboard shortcuts. 

Here's an ASCII art showing my idea of the icon:

[*]

And now, the ASCII art screenshot from the Studio editor view:

|----------------------------------------|[------------------]

| No match.                                    |[                       |

|----------------------------------------|[------------------]

|                                                    ||                      ||

[_____________________________][____________]

[*][PhotoPrinter.sdlxliff]

[1] [Sample Photoprinter] [............]

[2] [Way more photoprinters] [............]

Tooltip: {Select all segments}