It would be good if we could simplify the shared cell definition update to a right click>update from library as per element templates, materials, multi-lines etc etc...
The current workflow is, to say the least convoluted,
- open the dgn file (in which you want to replace the pattern cell)
- open Element>Cells
- detach an attached cell library
- make sure the option Use Shared Cells is checked
- activate and place the shared cell that is used in the pattern (so that there is at least one instance in the file)
- uncheck the option Use Shared Cells
- attach the cell library that contains the replacement cell
- select/activate the corrected cell (click the placement button in the Cell library dialog)
- activate the replace cell command
- set the following:
method: Replace
mode: Global
- identify and accept the visible shared cell
- the pattern cell should be replaced now.
- update the view
- the pattern cell should now be updated