I would love to be able to quickly organize photos into albums. Pixelmator Photo currently lacks the ability to drag one or multiple photos into an album on the sidebar which is possible in the native Photos app. Even the share sheet only features the option “Add to shared album” but not standard albums. I currently have to pop over to Photos, find where I was in the library, and then organize the images.
A huge +1 would be the ability to add and filter photos by meta tags