According to the Microsoft documentation, you need to have Basic access in VSTS in order to create Test Plans, however, when I log in with a user having Basic access, the link for adding a Test Plan is not there.
What additional access does this user need to be able to create Test Plans? The user is also an administrator of the team to which Test Plans need to be added.
Screenshots showing the MS documentation, the particular user's access level, how it should look according to MS and how it does look (with the "+" icon to add Test Plans not appearing when logging in as the user in question with Basic access).