### 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
minimap_resizer_color = Color(0, 0, 0, 0.65);
	}
	theme->set_icon("resizer", "GraphEditMinimap", theme->get_icon(SNAME("GuiResizerTopLeft"), SNAME("EditorIcons")));
	theme->set_color("resizer_color", "GraphEditMinimap", minimap_resizer_color);
	
	const int gn_margin_side = 2;
	const int gn_margin_bottom = 2;
	
	const int sm_margin_side = 10;
	Color graphnode_bg = dark_color_3;
	if (!dark_theme) {
		graphnode_bg = prop_section_color;
	}
	Ref<StyleBoxFlat> graphsb = make_flat_stylebox(graphnode_bg.lerp(style_tree_bg->get_bg_color(), 0.3), gn_margin_side, 24, gn_margin_side, gn_margin_bottom, corner_width);
	graphsb->set_border_width_all(border_width);
	graphsb->set_border_color(graphnode_bg);
	Ref<StyleBoxFlat> graphsbselected = make_flat_stylebox(graphnode_bg * Color(1, 1, 1, 1), gn_margin_side, 24, gn_margin_side, gn_margin_bottom, corner_width);
	graphsbselected->set_border_width_all(2 * EDSCALE + border_width);
	graphsbselected->set_border_color(Color(accent_color.r, accent_color.g, accent_color.b, 0.6));
	Ref<StyleBoxFlat> graphsbcomment = make_flat_stylebox(graphnode_bg * Color(1, 1, 1, 0.3), gn_margin_side, 24, gn_margin_side, gn_margin_bottom, corner_width);
	graphsbcomment->set_border_width_all(border_width);
	graphsbcomment->set_border_color(graphnode_bg);
	Ref<StyleBoxFlat> graphsbcommentselected = make_flat_stylebox(graphnode_bg * Color(1, 1, 1, 0.4), gn_margin_side, 24, gn_margin_side, gn_margin_bottom, corner_width);
	graphsbcommentselected->set_border_width_all(border_width);
	graphsbcommentselected->set_border_color(graphnode_bg);
	Ref<StyleBoxFlat> graphsbbreakpoint = graphsbselected->duplicate();
	graphsbbreakpoint->set_draw_center(false);
	graphsbbreakpoint->set_border_color(warning_color);
	graphsbbreakpoint->set_shadow_color(warning_color * Color(1.0, 1.0, 1.0, 0.1));
	Ref<StyleBoxFlat> graphsbposition = graphsbselected->duplicate();