[Lauris Olups]

I formatted my SD as internal via Marshmallow's built-in feature, but now I want to get it back to external. How can I do that? I have a rooted Cyanogenmode phone with TWRP.

[Aquila]

Settings > Storage then select the card and there's an option to reformat it. Make sure you move everything you want to keep of it, because it will wipe the card.

[Lauris Olups]

But the only option there is to format as portable!

[Aquila]

But the only option there is to format as portable!

Yep, that's the one you want.

[zuben el genubi]

FWIW:

I never formatted my SD card. I just shoved the same one in from the Oppo. I'm using it for media, so that isn't a problem.

What I did discover is that I could transfer other things between the card and the memory by using Solid File Explorer. Solid read all the card and could transfer to internal memory. Same folder ext to same folder int. It still saves media on the card with no fuss.