If you have custom support symbols added to your project settings, but they aren't displaying when you try to add them to your design via the 'Edit Structure' window, this could be for one of the following reasons.
Please note: If you have not already added custom structure support symbols to your project settings, you will not be able to display them. Find out how to add custom support symbols here.
Have you changed project settings?
If you change your active project settings and the custom support symbols are not present in the newly selected project settings, then they will not be available for selection.
You will either need to revert to the project settings which have the custom symbols included, or ask your organisation's Project Settings Administrator to submit an Alter Project Settings ticket to request the addition of these symbols into the required settings.
There may be an issue with your project settings
If you know your custom symbols are included in the project settings you are using in your design, and they still aren't showing in the 'Support symbols' section of the 'Settings' tab in the 'Edit Structure' window, then there may be an issue with your project settings.
Please ask your organisation's Project Settings Administrator to submit an Alter Project Settings ticket to raise this issue so our team can investigate and fix.