I forgot to mention why this would be useful.

It is apparent to detect the parent entities via the foreign keys but one cannot detect the child entities via the primary keys. A find usages by right-clicking on a primary key will not show its child entities either.

Could be a CTRL-drag which in other programs means add and turns the mouse cursor into a [+]. I don't think I want all entities every time, that would be annoying, but having the option to do sometimes would be clever.

CTRL-drag does not work, Soren. However, upon dragging an entity in the entity diagram and right-clicking on the entity opens a speed menu with the options "Show all entities reference by ..." and "Show all entities that refer ...".

The "Show all entities referenced by.." will add all parent entities and their joins to the ERD and the "Show all entities that refer.." will add all child entities and their join to the ERD.

That kind of makes this idea unnecessary. 

Hey @chris, 

Yeah I know it doesn't work right now, but it was a suggestion for how to implement the feature :) I'd like people who drag to have both options, both yours and the normal (single drag) one.