Hi again hcccs,
Since your last post, I have spent some time reading the downloadable pdf 'iOS Operating Manual' from the Air Nav Pro website (which is marked as 'old') but I can't find anything allowing you to change symbols for target aircraft. There is a link from the website to an online 'updated' version of the manual, but unfortunately despite multiple attempts over several days, the link doesn't appear to be working.
There is a 'get in touch with us' link from the Blog Page on the Air Navigation website, and as Paul says, they also have a Facebook page, with a messaging facility. I have sent a message to them via the website link to advise that the link to their online manual doesn't work and asking them whether the change you want to make is possible, but as a 'non-user' they might not reply to me, so probably best to get in touch with Air Navigation yourself via either of those options and see what they say. Please let us know how you get on.
Regards
Peter