### Godot version

v4.1.1.stable.official [bd6af8e0e]

### System information

Godot v4.1.1.stable - Ubuntu 22.04.2 LTS 22.04 - Vulkan (Forward+) - integrated Intel(R) UHD Graphics 615 (AML-KBL) () - Intel(R) Core(TM) i3-10100Y CPU @ 1.30GHz (4 Threads)

### Issue description

Summary: When editing the subregion of a StyleBoxTexture, it shows me the entire spritesheet of the Atlas texture, instead of the selected portion of the atlas, making it difficult (and non-intuitive) to correctly select the subregion I need. 

What I expect: I understand that the sub-region may be used to emulate the behavior of a nine-patch. So I would expect to see there the subregion that i selected previously from the Atlas as the texture to be shown.

I have only tested this in a Panel Container

### Steps to reproduce

I found this problem when doing these steps:

- Add a PanelContainer node
- In the inspector select Theme Overrrides -> Style -> new StyleBoxTexture
- In the texture of the StyleBoxTexture select new AtlasTexture
- Dropped the spritesheet in the Atlas of the AtlasTexture
- In Region of the AtlasTexture, selected Edit Region and drew the rectangle on the texture i want:
![image](https://github.com/godotengine/godot/assets/1207326/2e9624b1-63bc-4267-8d7f-59e82df7896e)

- Back in the StyleBoxTexture options, in Sub-Region, clicked on Edit Region to select the nine-patch region i need
- Here is where the region editor shows me the entire spritesheet and not the sub-texture i selected from the atlas. The image below shows the axis correctly positioned for the nine-patch to work, but it is not intuitive because it has to be positioned without seeing the correct texture, making it difficult to finetune for some textures.

![image](https://github.com/godotengine/godot/assets/1207326/a5023afd-7e4b-47c8-adfc-03fda7f6301b)


### Minimal reproduction project

N/A
float new_margin = 0;
				if (snap_mode != SNAP_GRID) {
					if (edited_margin == 0) {
						new_margin = prev_margin + (mm->get_position().y - drag_from.y) / draw_zoom;
					} else if (edited_margin == 1) {
						new_margin = prev_margin - (mm->get_position().y - drag_from.y) / draw_zoom;
					} else if (edited_margin == 2) {
						new_margin = prev_margin + (mm->get_position().x - drag_from.x) / draw_zoom;
					} else if (edited_margin == 3) {
						new_margin = prev_margin - (mm->get_position().x - drag_from.x) / draw_zoom;
					} else {
						ERR_PRINT("Unexpected edited_margin");
					}
					if (snap_mode == SNAP_PIXEL) {
						new_margin = Math::round(new_margin);
					}
				} else {
					Vector2 pos_snapped = snap_point(mtx.affine_inverse().xform(mm->get_position()));
					Rect2 rect_rounded = Rect2(rect.position.round(), rect.size.round());
					if (edited_margin == 0) {
						new_margin = pos_snapped.y - rect_rounded.position.y;
					} else if (edited_margin == 1) {
						new_margin = rect_rounded.size.y + rect_rounded.position.y - pos_snapped.y;
					} else if (edited_margin == 2) {
						new_margin = pos_snapped.x - rect_rounded.position.x;
					} else if (edited_margin == 3) {
						new_margin = rect_rounded.size.x + rect_rounded.position.x - pos_snapped.x;
					} else {
						ERR_PRINT("Unexpected edited_margin");
					}