My first ever Blender script so, GOOD LUCK.
This just isolates tools I use for plush patterning, automates a step or two, and most importantly: Exports the UV map image at real world scale for 3D printing. You will still need to manually name edit and layout your pieces in image editing software.

Also this thing was made with me shoving my programming logic and steps from my understanding of C++ into an AI to basically translate it into Blender Specific and Python language and interrogating it to tell me how to do shit or what to use for classes & such. If you are a human being with Knowledge:tm: please feel free to remake this without it being attached to AI slop.

How to install (Blender 4.3.2 not tested for other versions)

Sizing!

Select your object that is ready for sewing seams and you can set the size using the length or height! (based on the model bounding box)
If you write in both fields, the height will take priority.
This will help you resize your Plush to real world scale in Blender so you can use the measure tool in object mode on it to measure like, the bottom of a foot, then scale the exported UV map until the foot on it is the same size and* blam. You've scaled your pattern and should get the size you set when you sew it.

Tip: If you can't find your model or if it's too large/small/off in the void Select your object and use View -> Frame Selected

Mark your seams in edit mode to use this tool

Select your object and go into EDIT MODE.
Use Edge Selection Mode to select edges of your mesh (Or make new ones with the Knife tool) and mark your seams

Check UVs

SELECT your object.
Clicking the Check UVs button automatically moves you to a UV Editing tab and puts you into edit mode with all faces selected.
This shows you the UV map. It only displays what is selected in edit mode.
Make sure you unwrap your plush UVs with "Unwrap Plush UVs" button or use "Live Unwrap Toggle" while you're cutting your seams.

Unwrap or Live Unwrap

These buttons just make it easier for those unfamiliar with blender to unwrap their selected object without messing with keyboard shortcuts or submenus.
Live unwrap updates as you add seams (recommended - Automatic Unwrapping)
Unwrap only unwraps when you tell it to after making changes. (Manual Unwrapping)
You can find Live unwrap under the Overlay settings and UV unwrap under UV -> Angle Based

Export UV Map based on your plush dimensions (May not work tbh)

Click the x2 scale toggle for your UV map to export at a 300 DPI printable scale (You'll still have to arrange the UV Islands manually in external image editing software)

To get it to mostly work you need to export your base UV map at 2550 x 2550px, or set a blank 2550px image as the texture.
THEN the x2 scale button might work. But I can't guarantee. Make sure you measure the pieces to confirm scale.

If that doesnt work:
Use the measure tool in object mode on it to measure like, the bottom of a foot, then scale the exported UV map until the foot on it is the same size and* blam. You've scaled your pattern and should get the size you set when you sew it.

(My test with exporting with this made my image export for the plush size I wanted. But may need further testing.)

After you export the UV map, set up a new material

Click on the Base Color node of your material, and select 'Image Texture'

Go to the Texture Paint Tab and label your model, draw alignment marks, & mark nap direction manually.

Save the image and edit it in image editing software