The only way I know is:
- in CM, make a clone of the asset;
- rename the clone opening it in Explorer and the value of the "username" tag from "AssetName" to "AssetName Clone";
- in Surveyor, replace the asset with the clone using the mass replacement function(*), then save the route;
- in CM, delete the clone
- in Surveyor, select "Delete missing assets"(*)
- save the route.
This method only works if:
(*) the asset can be replaced through the "Replace" function: mass replacement of bridges, multiple tracks and some other asset types is not allowed;
(**) you have no missing assets beside the clone, otherwise you will also delete any other missing asset.