You can easily modify a saved workspace with the following procedure:

1.Load the workspace you want to modify, selecting the Merge in Current Window option and wait until the loading completes.

2.Change what you want in the workspace, e.g. search criteria etc.

3.Save the workspace with the same name, confirming you want to overwrite the existing workspace. IMPORTANT: if your workspace should keep the search criteria, make sure you ticked the Include Searches option!