To Open a Main Task in a Floating Toolbox

In the Customize dialog ( File > Settings > Configuration > Customize ) on the Tools tab, expand the Main Tasks tab.
Do one of the following:

Expand the User Tasks section and expand the open DGN file.

or
Expand the User Tasks section and expand the DGN library.

or
Expand the Application Tasks section and expand the tasks.
Select the Main task that you want to open.
Right-click the Main task and select Open Task Toolbox from the pop-up menu.
The name in the toolbox's title bar has "- Main Task" appended to it.