[Plugin: Post Snippets] Nested Shortcodes

I use another plugin (Tubepress) that has a shortcode, but the parameters are quite complex, so I’m trying to use Post Snippets to create a different shortcode which is translated into the complex Tubepress shortcode.

Here’s the working TubePress shortcode

[tubepress mode="playlist" playlistValue="4D13522A2CD8309E"]

In Post Snippets I define a new shortcode:

Title is: PL
Variable is: playlist
Snippet is: [tubepress mode="playlist" playlistValue='{playlist}']

In my post I put:

[PL playlist=4D13522A2CD8309E]

What displays on my page is:

[tubepress mode="playlist" playlistValue='4D13522A2CD8309E']

rather than the nice video gallery that Tubepress should show.

How can I get this to work?

http://ww.wp.xz.cn/extend/plugins/post-snippets/