Copying TextAsset files from assets folder to streaming assets at runtime

Is there a way I can move/copy TextAsset files mainly localization files, from the assets folder to the StreamingAssets folder directly at runtime?

The normal asset folder does not exist at runtime.
You can have the text asset referenced in your scene , read the text and write it to the streaming assets folder.
Or you could have build pre / post process that copies the files over from the editor. (provided you don’t need some information that is only available at runtime)

What would be the implementation to write the text to the streaming assets folder? I thought that the StreamingAssets folder was read only. I am currently using Unity version 2018.4.5.
Additionally how would I go about building the post process that copies the files from the editor?
My apologies I am fairly new to Unity.

It depends on your target platform.
On Windows for example its a normal folder that you can read or write to.
On Webgl and andorid you only have access via the a webrequest so no write access.

If you need a folder for saving Application data you can use

or

Thous should be writable on most platforms.

The main question for me is why the asset dont live in the streaming assets folder in the first place?

I’m on a webGL platform. The textassets are actually in the streaming assets folder, they are .csv files. The objective is to change the text in some of them in the game, while the game is running and then save them to the streaming asset’s folder.
I did not know if this would be possible with the files being in the streaming assets folder throughout.