It is easiest to take a known symbol and modify it for your purposes since there will already be many options for attachments and information pre-defined where all you need to do is change the graphics.
A very simple symbol to modify is the surface finish symbol.
I am not saying that making symbols is easy... on the contrary. You need a bit of understanding of how to edit and save symbols, and even how to reliably retrieve them. Just don't bury them in the file structure where Creo is installed or you might loose them in the next version update.
Tell me what size you want the symbol and I can see if I can make one for you. Can I assume an inscribed balloon tangent to the triangle would be a good start? Are you manually entering the affected revision or do you need it to pick up a parameter?
