How do I safely downgrade Minecraft from 1.14 to 1.13?

I have made a village for the new mod TangoTek is making, but this mod will probably only be playable in 1.13.2. Does anyone know how to reload a world from 1.14.3 to 1.13.2 without destroying every block you have placed?

You can't, downgrading pretty much always destroys something and in this case it got example crashes when loading a chunk that contains a tile entity. You can try storing everything in structure blocks, but that might also not work. Maybe someone made a program to downgrade worlds from 1.14 to 1.13, but… you could just build in 1.12.2 and upgrade - Paraphrasing Fabian Röling in a comment