I think it means to be passive, not to assert your rights in every single situation, to allow someone else to call the shots, even in a situation where you think your way would be more efficent.
Vatranus is not a mitzvah its a midah. I don’t know what a good translation would be. But it means to not be makpid on things that people do or say to you.
You can be mevater on your kavod- meaning you allow someone who is supposed to give you honor in some way, to not.
You can be mevater on bad things that people do to you.
A rough English translation for vatranus would be “passivity” or “easy-going.” It means being willing to forgo something you are actually entitled to in order to avoid machlokes. It’s a very important mida since it helps you avoid ka’as.
While it might seem like a negative thing because we don’t want people to push us around. It’s not about being pushed around. It’s about choosing peace over argument. We need to decide when it’s important to stand ground, and when we just need to let go when something is not important,