Modal Backdrop Z-Index should be higher than Offcanvas Z-index.

[jeddtobee023]

By default,
$zindex-modal-backdrop: 1040;
$zindex-offcanvas: 1050;
$zindex-modal: 1060;

I think it should be like this:
$zindex-offcanvas: 1040;
$zindex-modal-backdrop: 1050;
$zindex-modal: 1060;

So that when a button in offcanvas supposed to open a modal, the offcanvas would not overlap to the modal backdrop.

[ffoodd]

I guess we need a separate variable for offcanvas' backdrop then, since offcanvas uses a backdrop too. @GeoSot am I right?

[GeoSot]

On a first thought, seems valid, as modal backdrop z-index is less that offcanvas
And if we go with this, we have to take a look on #34149

[mdo]

This was done awhile back.

bootstrap/scss/_variables.scss

Lines 1031 to 1039 in 63f75bc

	$zindex-dropdown: 1000 !default;
	$zindex-sticky: 1020 !default;
	$zindex-fixed: 1030 !default;
	$zindex-offcanvas-backdrop: 1040 !default;
	$zindex-offcanvas: 1045 !default;
	$zindex-modal-backdrop: 1050 !default;
	$zindex-modal: 1055 !default;
	$zindex-popover: 1070 !default;
	$zindex-tooltip: 1080 !default;