WhatsApp is testing a new way to make it easier to send long voice messages. And yes, we have seen this before
According to WABetaInfo , you can record voice messages without holding the microphone button all the time: just slide up to the padlock and speak at will. You can even take a look at the conversation history.
It is not possible to open a conversation with another person, however, nor write messages while recording. At the moment, this is present in version 2.17.80 for iPhone , and only appears for some users – it is a test.
1. It’s not possible to view a photo/video while you are recording a “locked” voice message. You have to use the 3D Touch action to view it (iPhone 6S and newer)
2. You cannot type a new message while you are recording a “locked” voice message. You have to end it to type a message.
3. While you are recording a “locked” voice message, you cannot turn to another chat. In some situations it is possible but the voice message will be deleted.
There are other limitations, but they look like bugs that will be fixed before the activation of the feature.