Dear @MikeyH ,
if you open directly the HmiDesigner from C:\Program Files\REX Controls\HmiDesigner 3.2.5\bin\HmiDesigner.exe you will not see any extensions.
You have to use the HmiDesigner.exe from the REXYGEN installation e.g., C:\Program Files\REX Controls\REXYGEN 3.0.6.17802\HmiDesigner\HmiDesigner.exe
This is also the way TrayMonitor opens the program. If you have any file association for *.svg, check whether it uses HmiDesigner.exe in the REXYGEN folder.
This is a known limitation, and we will try to solve it in a future version.
Best regards
Ondrej