Great! That's right!
In the USERCP_SHELL template each link is managed by the code (here is the Customize link example) :
HTML Code:
<if condition="$show['customizelink']">
<tr><td class="$navclass[customize]" nowrap="nowrap"><a class="smallfont" href="profile.php?$session[sessionurl]do=customize">$vbphrase[customize_profile]</a></td></tr>
</if>
For my custom page, I delete the "if" condition
(I don't know how to use the $show variable and, fortunately, I want to display this link for all members), I change the href and the do= variable. For the $vbphrase I create a custome vbPhrase.
It's no important but do you know how to use the $show variable?
Now I'll try to create my custom page