Flowers in shade are hard to come by. Nandina will do okay in some shade but in very deep shade may not bloom and berry well. If you move those plants take care to keep the soil moist as they will burn in sun without adequate soil moisture.
I the shade you might consider American Beautyberry but it is wider and lower growing...and deciduous. A perennial to consider is shrimp plant but the shade may be iffy for it to bloom if shade was the real reason the nandina was not flowering. I might try white butterfly ginger there. It dies to the ground with the first frost but produces fragran white blooms in the fall.
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