Sadly no 'arrows' appear at the corners which allow the pop-up to be resized.

Yeah not on chooseDirectory , but DirSelect is resizable

Do you know of any more extensive examples of DirSelect being used? My attempts to find these on the internet have failed.

I don't understand the question, examples doing what?

Its a real simple module to use

 perl -MTk -e " print tkinit->DirSelect(-width,5000 )->Show( shift ) "
+ D:\
[download]

And its written in perl, so its easy to understand/modify....