The reason focus is lost is that changing the property causes the construction script to run which in turn destroys and creates a different component, so after the change you're not selecting the same object anymore.
Result of pressing enter when editing text in a subcomponent (of an actor that exists in world) has different behavior than elsewhere in the editor.
Confirmed in 4.24 MAIN @ CL 7519848
Result: Cell Focus is lost.
Expected: Focus remains and the input is highlighted.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-77858 in the post.