### 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
graphsbposition->set_draw_center(false);
	graphsbposition->set_border_color(error_color);
	graphsbposition->set_shadow_color(error_color * Color(1.0, 1.0, 1.0, 0.2));
	Ref<StyleBoxEmpty> graphsbslot = make_empty_stylebox(12, 0, 12, 0);
	Ref<StyleBoxFlat> smgraphsb = make_flat_stylebox(dark_color_3 * Color(1, 1, 1, 0.7), sm_margin_side, 24, sm_margin_side, gn_margin_bottom, corner_width);
	smgraphsb->set_border_width_all(border_width);
	smgraphsb->set_border_color(graphnode_bg);
	Ref<StyleBoxFlat> smgraphsbselected = make_flat_stylebox(graphnode_bg * Color(1, 1, 1, 0.9), sm_margin_side, 24, sm_margin_side, gn_margin_bottom, corner_width);
	smgraphsbselected->set_border_width_all(2 * EDSCALE + border_width);
	smgraphsbselected->set_border_color(Color(accent_color.r, accent_color.g, accent_color.b, 0.9));
	smgraphsbselected->set_shadow_size(8 * EDSCALE);
	smgraphsbselected->set_shadow_color(shadow_color);
	graphsb->set_border_width(SIDE_TOP, 24 * EDSCALE);
	graphsbselected->set_border_width(SIDE_TOP, 24 * EDSCALE);
	graphsbcomment->set_border_width(SIDE_TOP, 24 * EDSCALE);
	graphsbcommentselected->set_border_width(SIDE_TOP, 24 * EDSCALE);
	graphsb->set_corner_detail(corner_radius * EDSCALE);
	graphsbselected->set_corner_detail(corner_radius * EDSCALE);
	graphsbcomment->set_corner_detail(corner_radius * EDSCALE);
	graphsbcommentselected->set_corner_detail(corner_radius * EDSCALE);
	theme->set_stylebox("frame", "GraphNode", graphsb);
	theme->set_stylebox("selected_frame", "GraphNode", graphsbselected);
	theme->set_stylebox("breakpoint", "GraphNode", graphsbbreakpoint);
	theme->set_stylebox("position", "GraphNode", graphsbposition);
	theme->set_stylebox("slot", "GraphNode", graphsbslot);
	theme->set_stylebox("state_machine_frame", "GraphNode", smgraphsb);
	theme->set_stylebox("state_machine_selected_frame", "GraphNode", smgraphsbselected);
	Color node_decoration_color = dark_color_1.inverted();
	theme->set_color("title_color", "GraphNode", node_decoration_color);
	node_decoration_color.a = 0.7;