Whatsapp: Export pictures from certain conversations
I think there is no native way of doing that, and I have not seen any app that does it.

From my experience, the best way is via WhatsappWeb. I used this quite a few times.


Select the target conversation, on the left.
Click on the conversation name, at the top.
Expand Media.
Make sure all files are loaded, by scrolling/waiting.
Select all files you want.
You can Forward, Download, etc.


I found the same idea here.