Create a searchable icon library?

The script I linked was for searching artboards (better fit for the OP's needs)....

If you need to search for the symbols in your documents Symbols palette, you can try the script below. It uses a searchable list box from the book ScriptUI for dummies by Peter Kahrel and the Symbols collection from the API (learn more). Whatever symbol you select in the dialog will be available in the script as the variable `symbol` (learn more).

Note: this does not search the actual symbols placed on the document artboard(s), just the base symbols in the palette...

Finally, I'm not sure what you plan to do with the selected symbol after selecting so let us know and we can help you with the next step(s) if you need it. Cheers!

// get the current document
var doc = app.activeDocument;

// get symbols from current document
var symbols = [];
for (var i = 0; i < doc.symbols.length; i++) {
  symbols.push(doc.symbols[i].name);
}

// show symbol picker
picked = picker(symbols);

// select symbol for later use
var symbol = doc.symbols.getByName(picked);

// alert choice for debugging
alert("You picked symbol...\n" + picked + "\n" + symbol);

// "type-ahead" listbox found in ScriptUI for dummies by Peter Kahrel (pgs. 37-38)
// https://creativepro.com/files/kahrel/indesign/scriptui.html
// NOTE: If you document has lots of symbols you may want to read the "Processing long lists" section (pgs. 39-40)
function picker(arr) {
  var w = new Window('dialog {text: "Document Symbols", alignChildren: "fill"}');
  var entry = w.add("edittext {active: true}");
  var list = w.add("listbox", [0, 0, 250, 250], arr);
  list.selection = 0;
  entry.onChanging = function () {
    var temp = this.text;
    list.removeAll();
    for (var i = 0; i < arr.length; i++) {
      if (arr[i].toLowerCase().indexOf(temp) == 0) {
        list.add("item", arr[i]);
      }
    }
    if (list.items.length > 0) {
      list.selection = 0;
    }
  };
  // We need the button to catch the Return/Enter key (CC and later)
  w.add("button", undefined, "Ok", { name: "ok" });
  if (w.show() != 2) {
    return list.selection.text;
  }
  w.close();
}

@jodmcc49  Thank you for the link. Unless something has changed, I don't see a way to search a library like, as an example for the "magnifying glass" icon. Seems you just scroll until you see it? 

@jduncan Thank you, this is exactly what I was looking for (no pun intended)!