Finder - move selected files to "_OLD" folder

This should do it :)

function moveFiles({ sourcePaths, targetFolder }) {

    for(let sourcePath of sourcePaths) {
        var sourceFilename = sourcePath.split('/').slice(-1)[0];
        var targetPath = targetFolder + '/' + sourceFilename;

        sf.file.move({
            sourcePath: sourcePath,
            destinationPath: targetPath,
        });
    }

}

function main() {

    var sourcePaths = Array.from(sf.ui.finder.selectedPaths);
    if (sourcePaths.length === 0) return;

    var sourceFolder = sourcePaths[0].split('/').slice(0, -1).join('/');
    var targetFolder = `${sourceFolder}/_OLD`;

    sf.file.directoryCreate({ path: targetFolder });

    moveFiles({
        sourcePaths,
        targetFolder,
    });
}

main();