Since there is a special callback for assigning the name from the search box, and the callback doesn't call an operator or something else that would do an undo push, I think the solution is to do it manually here. Another option would be adding the button flag "UI_BUT_UNDO", which isn't set by default for search buttons, but that gives us ugly names for the undo steps, so an explicit push is better in this case. Differential Revision: https://developer.blender.org/D11190