How to create a custom panel inside wp admin dashboard where we can insert media to specified posts in bulk? Here is the illustration:
As shown on the image above, it list all available media on the left and provide the box where we can insert post id to attach the media to. And we can then bulk insert media to the specified posts by hit the attach buttons after we specified the post id for each listed media.
I had spent several days trying to figured out how to do it, had tried some plugins also media library editing, but still can not found the answer.