paul kgyy writes:

What if I don't have it visually, but it shows up on my traffic
display?

"Negative contact."

It's good if you have it on your traffic display, but you technically need
visual contact in order to assume responsibility for separation.

there's also the thought that if you don't have it visually, you don't
really "have it" - i.e. the electronic display does not provide as
good separation info as actually seeing the traffic with your Mark 1
eyeball.

Yes, especially since TCAS displays are not very accurate in azimuth.