dynamic save path

Hello,

I want to save every pdf file to user folder based on their username.

For example: if user X fills a form, pdf is generated and saved automatically to directory wp-content/user/X, user Y to wp-content/user/Y and so on. I know that directory must be created beforehand.

I've tried to use this shortcode but with no luck:
[e2pdf-save id="1" name="%name%" dir="wp-content/user/{user:user_login}/"]

I don't know how to declare this variable {user:user_login} cause i tried to use static username and it works flawlessly.
Also, when using this variable outside shortcode (in Success Message) i'm getting my username correctly.
Is it variable itself, is it wrong syntax? Is it doable at all it this way? Please help.

Thank you for quick reply, I'll be waiting for your response.