Hi @user41905425 - Yes, there is not much information about the cookie - test_amcv_cookie_write.
This cookie is being created by visitorapi js file.
It is meant for -
TEST_AMCV_COOKIE_WRITE |
Adobe Inc. |
Determines whether the user has accepted the cookie consent box. |
Session |
If needed, you can refer the code on github - https://github.com/Adobe-Marketing-Cloud/id-service/tree/master/lib
Hopefully, this answers your query!