Welcome to the forum, Christopher. A couple of points:
Ignition uses Jython for scripting. Your
{[~]FOLDER NAME/TAG_NAME.value} || {[~]FOLDER NAME/TAG_NAME.value}
is an expression and follows the documented rules for Expression Language and Syntax | Ignition User Manual (where you will find the logical OR syntax documented). You can think of Ignition's expression language as being like a spreadsheet's functions.
Expressions often involve one or more other values that are used to calculate a final value. In most cases, expressions only return a value.
In Excel you would use VBA (Visual Basic for Applications) for scripting and in Ignition it would be Jython.
For posting code here, please see Wiki - how to post code on this forum.