FreeCAD

I’ve used it to pattern cuts for a laser cutter.

While it’s possible it’s very buggy especially with curvy designs. There’s a function called Flatten to SVG which helps with this step but it requires a lot of tuning of the model, to get the export right.

A great example is a hole in the design, perhaps for a button. If done wrong the button hole is the main solid and the rest of the design is not solid. Plus you’ll have so much extra lines that cleanup is not fun.

For me I need to do it this way since the pattern is mated to a 3D print so having every 1:1 is a must. But if you are doing it for other reasons, I would look elsewhere.

Tech drawings is another way to export an design too if you want to go through with it anyways.

It sounds like you are looking for more of a pattern designing tool. There are open source projects that might be more suited to this than freeCAD. Try searching online for “open source textile pattern software”

I can’t vouch for this program/project as I am not involved nor have I used it; but Velentina sounds like it is capable of doing what you mentioned.

The sketchers in freeCAD can be used to draw and constrain the patterns, and then print them to scale and cut them out to see how it works.

(Note I have not tried to print to scale from freeCAD specifically but I would imagine it is more then capable of doing so assuming your sketches are smaller then the paper you are printing on)

Of course freeCAD can be used to do the physical modeling but I am unaware of any tools that would specifically assist you for textile pattern designs. The closest tool that I am aware of is the sheet metal workbench.

Hopefully this was helpful.

Someone else might be able to suggest a freeCAD specific solution but this might help get you started.