Andrew,
My apologies.  I have installed the latest release of inkscape on computer.  I followed the instructions provided in the tutorial to install the inkstitch extensions but the inkstitch extension does not appear when I try to use it.  I downloaded the zipped file, and extracted it to the inkscape extension directory (C:\Users\(me)\AppData\Roaming...) as instructed in the tutorial.  It appears that the extensions are extracted.  I received no errors or warnings.  I'm not sure how to resolve this.
I have tried uninstalling and reinstalling several times.  It seems that even after uninstalling inkscape, the extensions remain since when I try to re-extract them and place them in the previously noted directory, I get a windows showing the files already exist and am asked to keep or replace them.  I have tried both keeping and replacing to no avail.
As I said my computer is running the current release of Windows 10 (x64), I have 32 Gb of RAM, 2 - quad core Xeon processors and GTX 1050 Ti video card.  If there is any additional information you would need just let me know and I will be happy to provide it.
Regards,
Norm