1. go to /admin/build/pages
2. set path to /user/%user/tasks/%tasks if you want to overwrite tasks for /user/%user (eg. /user/%user/edit), for node use /node/%node/tasks/%tasks, it shouldn't actually matter how you name last two elements of the path
3. assign appropriate context for first argument (User: ID or Node: ID), for third one (%tasks) select String and check 'Get all arguments after this one' in its settings
4. no menu entry
5. !!! be sure you saved it before adding the pane to it otherwise you won't see checkboxes
6. add pane 'Local tasks proxy' from 'Page elements' and select which local tasks should be rendered using this panel
