Thank you!  This is exactly what I wanted.  The hint about Adobe is informative - not all LucidChart users know Adobe so you guys could be more clear about these kinds of assumptions.

This does not work for Entity Relation Diagrams.

Even if the curve line is set as a default for the document every new line created from dragging out of an entity will be straight by default and the user has to manually set it to curved.

Thanks for posting in the Lucidchart Community! Maxime is correct - custom line style settings do not apply to ERD shapes. This is the intended behavior so you will have to manually change the style of lines from ERDs. However if you drag out a line from a non-ERD shape and connect it to an ERD shape then custom settings will apply. 

Thanks you save my time.

Same issue but found a solution. If you have a Lucidchart diagram (specifically that has never been edited in Lucidspark) the default line shaping works as specified above. HOWEVER if you edit the Lucidchart with Lucidspark the defaulting when you go back into Lucidchart breaks and takes it's default shape from whatever is set in the Lucidspark. You are welcome!

Hi @john t104 thanks for posting another workaround! To anyone interested in trying this please note that this workaround requires the universal canvas feature which is limited to enterprise accounts only. Thanks for sharing your ideas!