U can use the flatten-operation on each parameter (input/output-plug) directly. Just right-click on the text beside the plug and have a look what is coming up. Depending on the type, different options come up.
Graft / Simplify / Flatten are always part of the choice because the are used on the passed DataTree.
At the first look, “Flatten” is the inverse of “Graft”, but its not. The inverse of “Graft” is “ShiftPath”.
looks like u are a beginner? U should have a look up for DataTree.
The use of flatten is kind of useful, but should be used with care. I guess it is ok for beginners to use.
But, If u want to go further u should avoid it soon, and replace it with the “shiftPath” component, which is used to lower the branching of a tree in a good manner.
Using a single flatten in a definition may destroys the ability to use a “single-element”-solution in an other scenario where “multiple elements” are solved with the same method at the same time, which is extremly useful for more complicated tasks.