If we create a fence, Clip Volume or Clip Mask pressing the button "By Element" then MicroStation should ask us if we want to Retain original element. (add that parameter in the Tool Settings)

For example, if you create a wipeout (Clip Mask) in AutoCAD (wipeout command) and you choose "polyline" in the command line then the next parameter is "Remove polyline"(Yes/No) .

A lot of times I have to create a copy of the element before pressing the "By element". If I create a named boundary from a "By element", when I remove the named boundary then removes that element as well.

Another possibilty is 2 buttons:

[By element]

[Copy By element]