Using RegEx to sort text in a variable?

[ComplexPoint]

Or, in an 'Execute JavaScript for Automation' action:

(using regexes here, since you expressed curiosity about that, though I would probably reach more quickly for split functions myself)

Note: The higher-order mappendComparing function supports n-ary sorts by deriving a comparator function from a list of property-getting functions.

Sorted filenames.kmmacros (19.9 KB)

Full source of the Execute JS4A action
(ES6 JavaScript, so Sierra onwards – for [Yosemite onwards] ES5 JS, past into the Babel JS repl at https://babeljs.io/repl/)

(() => {
    'use strict';

    // GENERIC FUNCTIONS -----------------------------------------------------

        // lines :: String -> [String]
        const lines = s => s.split(/[\r\n]/);

        // mappendComparing :: [(a -> b)] -> (a -> a -> Ordering)
        const mappendComparing = fs => (x, y) =>
            fs.reduce((ord, f) => (ord !== 0) ? (
                ord
            ) : (() => {
                const
                    a = f(x),
                    b = f(y);
                return a < b ? -1 : a > b ? 1 : 0
            })(), 0);

        // sortBy :: (a -> a -> Ordering) -> [a] -> [a]
        const sortBy = (f, xs) =>
            xs.slice()
            .sort(f);

        // toLower :: Text -> Text
        const toLower = s => s.toLowerCase();

        // unlines :: [String] -> String
        const unlines = xs => xs.join('\n');


        // COMPARABLE FILE NAME PARTS --------------------------------------------

        const stemPreNum = s => toLower((s.match(/^[^\d\.]+/) || [''])[0]);

        const stemNum = s => parseInt((s.match(/^\D+(\d+)\./) || ['', '0'])[1], 10);

        const suffix = s => (s.match(/\.(\w+)$/) || ['', ''])[1];

        // TEST ------------------------------------------------------------------
        return unlines(
            sortBy(
                mappendComparing(
                    [stemPreNum, stemNum, suffix]
                ),
                lines(
                    Application('Keyboard Maestro Engine')
                    .getvariable('fileNames')
                )
            )
        );
    })();