vibrate when outgoing call answered

I have never heard of this feature. Most likely no one has answered because it doesn't exist on GrapheneOS.

Of course, you can install a third-party dialer app if you know of one that has this feature.

ikariwths Hello, do you know how [to] enable vibrate when outgoing call answered?

I think may not be a feature of the built-in AOSP dialer. That feature might be supported by other dialers that could be installed.

ikariwths anyone?

The GrapheneOS community is world-wide, which means that people have a wide variety of sleep schedules. Also, people have various work and family responsibilities. Overall, while some questions may receive answers very quickly, it is arguably not a best practice to "bump" a question in less than 24 hours. This forum is not a real-time chat room. Those do exist for GrapheneOS (source).

ikariwths What is the fastest way to inform the developers about its importance? Do the grapheneos developers have a page where we can ask for future features?

It is possible to file a feature-request issue on the GrapheneOS issue tracker. However, personally I suspect the developers will not add this feature. GrapheneOS is focused on security and privacy, which consumes most of the development resources, and does not make a lot of UI enhancements. Maintaining and testing changes while quickly adopting upstream changes is laborious for even small changes.

ikariwths With this option when you call someone you don't need to hold the phone to your ear until they answer.

I sometimes use the speakerphone button in such a situation. And, again, it is possible that third-party dialer apps may have the feature you are looking for.