To Move a Toolbox Using Cut and Paste

In the Customize dialog ( File > Settings > Configuration > Customize ) , click the Tools tab.
Expand the User Tools section and expand the open DGN file.
Select the toolbox that you want to move.
Do one of the following:

Click the Cut icon.

or
Right-click the toolbox and select Cut from the pop-up menu.
Select the open DGN file or toolbox to which you are moving the toolbox.
Do one of the following:

Click the Paste icon.

or
Right-click the open DGN file or toolbox and select Paste from the pop-up menu.