In this example:

The 1st one is a Decision, the other are Input Data.
Experienced DMN practitioner may know that a decision logic can only happen to Decision or BKM node, hence one could distinguish potential Input data node by not having decision logic (context in the example). But also what about Decision or BKM for which you didn't write the decision logic yet?

PLease consider distinguished icon for DRG Elements.
For example
leave Input Data with the filled circle
Decision: filled square
BKM: filled trapezoid.

Thanks