'handles.inputData' contains a period, which is not allowed in variable names. That makes it an expression that when evaluated returns a variable. If you assign the output of that expression to an identifier, that identifier must be a valid variable name.
> In Variable Editor both handles and handles.inputData are listed as "1x1 > struct". Furthermore, they are both data "things" in matlab which contain > multiple data structures and arrays and cell arrays. What makes the one > different from the other?
"Ben Ruppel" is the name you use to post to CSSM.
"The person that posts to CSSM using the address 'firstname.lastname@example.org' " refers to you, but it is not your name. If I "evaluate" that expression by searching CSSM, I can find your actual name. [Not the best of examples, as anyone can spoof their email address, but hopefully good enough for illustration purposes.]
> Is there a way for me to make handles.inputData a scalar struct variable?
For purposes of SAVE? Not without assigning it to a variable.
> Or is the problem more that handles.inputData is an expression? If that > is the case, is there a way to point to this data structure that does not > count as an expression?