At this time, there isn't support for removing images from the "My Photos" panel once they're added to a project.
However, this is a popular request and one that we will have planned to introduce in an upcoming release.
We always appreciate hearing feedback from our users. Let us know if you have additional requests!
Please always feel free to add any feedback or suggestions here: https://mimeophotos.canny.io/feedback
Once you vote, you'll be emailed once we've updated or added the requested feature.