JS script, which helps delete all inactive (gray) applications from NewRelic. Run script in JS console in Application view.

Delete all inactive applications from NewRelic

var yourId = 357957

var table = document.getElementById('apptable');
var rowLength = table.rows.length;

for(var i=1; i<rowLength; i+=1){
    var row = table.rows[i];
    var cellLength = row.cells.length;

    if(row.cells[0].childNodes[0].getAttribute('alt') === 'Unavailable') {
        var id = row.getAttribute('id').substring(12)
        $.post('https://rpm.newrelic.com/accounts/'+yourId+'/applications/'+id, {'_method':'delete', 'format':'json'})
    }
}