bootstrap 4 trigger modal js code example
Example: bootstrap 4 start modal in modal
var modal_lv = 0;
$('.modal').on('shown.bs.modal', function (e) {
$('.modal-backdrop:last').css('zIndex',1051+modal_lv);
$(e.currentTarget).css('zIndex',1052+modal_lv);
modal_lv++
});
$('.modal').on('hidden.bs.modal', function (e) {
modal_lv--
});