I wish I could say that worked but sadly it did not, I had to resort to adding the SVG to the menu item’s label inline, not ideal for a client website, but it’ll to do for now.
Thank you for your attempts to help, if you have any other ideas I’m all for trying them.
Regards.
After adding this to the functions.php file I still have the ongoing issue of after selecting the SVG from my media library it shows no thumbnail, and does not appear when the menu is outputted in the frontend.
Thank you for your help though. Very much appreciated.