How to download remote index in Nexus OSS 3.2?

I successfully installed Nexus OSS 3.2, but I get no search results, for example for "junit". Also under Browse / Components / Maven Central are no components listed.

I found NEXUS-9563 with following answer:

This means that the search indexes from Central haven't been downloaded. Have you set "Download Remote Indexes" to "true" in the central proxy repository's configuration?

But I can't find an option "Download Remote Indexes" in Nexus OSS 3.2. See proxy settings for Maven Central:

I tried:

• Button Rebuild index:

  The Rebuild Index button allows you to drop and recreate the search index for the proxy repository, synchronizing the contents with search index. This button is only available for proxy repositories.

• Task of type Publish Maven indexes:

  Maven indexes can be used to download an index of available components to a client including a developer’s IDE, for example. The task publishes the index for all or a specific Maven repository.

but nothing downloaded the remote index.

How can I download the remote index of a proxy?