You can write a Codeunit which can batch update the Object table and update the modification date field. You can then write your own page (or form if you are using only C/SIDE) with a button to invoke the codeunit. You could, for example, set filters on that page to determine which objects are updated.
If you want to import and export objects, it is a little tougher. In NAV 2013 you can use the command line interface for C/SIDE. In earlier versions, I think the only way to do this is to use CFront which can import and export FOB files.