LR Mobile: Remove from collection.
I currently create a collection for images needing review and open it in LR Mobile. I want to hone the collection by removing photos that no longer need my attention.
in Lightroom mobile grid view, hold your finger on the image you wish to remove. A menu will appear, which contains a "Remove" option. This removes the image from the collection, but the image will remain in your catalog on Lightroom desktop.