The following might help. You will need the "de-glazing tool" described in the text. Contact GT Window Products Limited, details on pdf below.
http://www.whiteline.co.uk/wp-content/uploads/2016/08/Fortrezz-Sidelite-Clip-De-Glazing-Tool-Instructions.pdf
https://www.gtwindowproducts.co.uk/new_product_sheets/Securi-Clip/halo_system_10_external.pdf
RoyD, September 2020