MicroStation has a command to bring to front elements Edit > Bring to front but it does not have a command to send to back, this task can be accomplished in the following way.
1- In the following image of different elements the White rectangule is placed in front of the others. So we are going to select it.
2- We are going to open Level display window and turn on all the levels.
3- Now we are going to use Element selection Invert option we will select every element in the model.
4- Going to Edit > Bring to Front command.
5- Now we will use View Previous command to restore the level display we had at the start of the process.