I assume you are creating a new plugin or node with a sidebar?
I also assume you mean this "shade" is visible (blocking) at "certain times" (like when a nodes edit panel is open) - is that your issues? Are you trying to keep the side bar accessible while editing a node?
In the doc you linked to:
enableOnEdit (optional) If set to true, this tab will be accessible whilst the edit dialog is open. Default: false.
this means the sidebar can be accessed at those times it would otherwise be blocked. e.g. when editing a node or searching, some side bar operations are (and should be) blocked.
At the moment, it only appears when I double click a flow or a node, is there any event that I can call the "RED.sidebar.addTab" without a need to double click on flow. I mean as soon as the app is ready to use, the new tab can be added ?