Q.Shade perennials zone 5 southern CT
Planted a garden few years ago that gets more shade than I realized – Tall phlox, monkshood and Salvia doing well but echinacea and black eyed Susans are lackluster and growing smaller so will transplant to sun. Question is, what to plant behind salvia, next to phlox and in front of monkshood? Probably enough space for 7 healthy plants. Wondered if enough sun for liatris?
Much appreciated!!!

Here are some great articles that have lots of shade loving plant ideas to help you get started with this project!
https://www.gardeningknowhow.com/special/shade/shade-tolerant-flowers.htm
https://www.gardeningknowhow.com/special/shade/finding-a-shade-loving-plant.htm
https://www.gardeningknowhow.com/special/shade/plants-for-shady-borders.htm
https://www.gardeningknowhow.com/garden-how-to/info/partial-shade.htm