Echoing floral_uk, this seems like Dogwood.

Carefully break a leaf in half across the midrib, but don't separate the halves by more than a centimeter. Does the sap harden into "spider webs"?

You have the incredibly beautiful Pagoda Dogwood https://mortonarb.org/plant-and-protect/trees-and-plants/pagoda-dogwood/

When it goes dormant carefully move it to its new location.

I'd agree w/sam. They transplant quite easily (when dormant of course), and prefer at least some shade. Birds devour the ripe berries in a hurry -- I've even seen a chipmunk climbing in the branches eating berries.

Thanks all! I shall certainly try to move it carefully. I saw such blooms as shown earlier in the spring - so that clinches it.