### 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
style_tree_hover->set_border_width_all(0);
	theme->set_stylebox("hover", "Tree", style_tree_hover);
	Ref<StyleBoxFlat> style_tree_focus = style_default->duplicate();
	style_tree_focus->set_bg_color(highlight_color);
	style_tree_focus->set_border_width_all(0);
	theme->set_stylebox("selected_focus", "Tree", style_tree_focus);
	Ref<StyleBoxFlat> style_tree_selected = style_tree_focus->duplicate();
	theme->set_stylebox("selected", "Tree", style_tree_selected);
	Ref<StyleBoxFlat> style_tree_cursor = style_default->duplicate();
	style_tree_cursor->set_draw_center(false);
	style_tree_cursor->set_border_width_all(MAX(1, border_width));
	style_tree_cursor->set_border_color(contrast_color_1);
	Ref<StyleBoxFlat> style_tree_title = style_default->duplicate();
	style_tree_title->set_bg_color(dark_color_3);
	style_tree_title->set_border_width_all(0);
	theme->set_stylebox("cursor", "Tree", style_tree_cursor);
	theme->set_stylebox("cursor_unfocused", "Tree", style_tree_cursor);
	theme->set_stylebox("title_button_normal", "Tree", style_tree_title);
	theme->set_stylebox("title_button_hover", "Tree", style_tree_title);
	theme->set_stylebox("title_button_pressed", "Tree", style_tree_title);
	Color prop_category_color = dark_color_1.lerp(mono_color, 0.12);
	Color prop_section_color = dark_color_1.lerp(mono_color, 0.09);
	Color prop_subsection_color = dark_color_1.lerp(mono_color, 0.06);
	theme->set_color("prop_category", "Editor", prop_category_color);
	theme->set_color("prop_section", "Editor", prop_section_color);
	theme->set_color("prop_subsection", "Editor", prop_subsection_color);
	theme->set_color("drop_position_color", "Tree", accent_color);
	
	Ref<StyleBoxFlat> category_bg = style_default->duplicate();
	category_bg->set_bg_color(prop_category_color);