Fabric.js Canvas - Make one type of object always stay below the other

I am working on a project in which I have to add rectangles and add triangles into those rectangles. I get the currently selected rectangle using this

const rect = canvas.getActiveObject().aCoords

then I check if the mouse click is in the rectangle and if true I add a triangle.

const x = event.pointer.x
const y = event.pointer.y
if (rect.tl.x + 20 < x < rect.br.x - 20 && rect.tl.y + 20 < y < rect.br.y - 20) {
            var points = regularPolygonPoints(3, 10);
            var myPoly = new fabric.Polygon(points, {
                stroke: 'red',
                left: x,
                top: y,
                strokeWidth: 2,
                strokeLineJoin: 'bevil'
            }, false);
            canvas.add(myPoly);
        }

The problem is the whenever the rectangle is selected it comes on top of all the added triangles and only after I click away to deselect the rectangle, the triangles appear from beneath.

Please see the images below to better understand

Unselected

Selected rectangle coming on top of the triangles

What I want is that even if the rectangle is selected it always stays below the triangles. Any help will be appreciated. Thank You.

from Fabric.js Canvas - Make one type of object always stay below the other