### 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
edited_margin = 3;
						prev_margin = margins[3];
					}
					if (edited_margin >= 0) {
						drag_from = mb->get_position();
						drag = true;
					}
				}
				if (edited_margin < 0 && snap_mode == SNAP_AUTOSLICE) {
					Vector2 point = mtx.affine_inverse().xform(mb->get_position());
					for (const Rect2 &E : autoslice_cache) {
						if (E.has_point(point)) {
							rect = E;
							if (Input::get_singleton()->is_key_pressed(Key::CMD_OR_CTRL) && !(Input::get_singleton()->is_key_pressed(Key(Key::SHIFT | Key::ALT)))) {
								Rect2 r;
								if (atlas_tex.is_valid()) {
									r = atlas_tex->get_region();
								} else if (node_sprite_2d) {
									r = node_sprite_2d->get_region_rect();
								} else if (node_sprite_3d) {
									r = node_sprite_3d->get_region_rect();
								} else if (node_ninepatch) {
									r = node_ninepatch->get_region_rect();
								} else if (obj_styleBox.is_valid()) {
									r = obj_styleBox->get_region_rect();
								}
								rect.expand_to(r.position);
								rect.expand_to(r.get_end());
							}
							undo_redo->create_action(TTR("Set Region Rect"));