How to include/exclude only certain segments into TM

I am proofreading a large translation (which came with its own TM) and would like to save some useful segments for future use into my own TM. If I attach my own TM to the project, presumably the whole translation will be included in my TM when I choose “update main translation memory”/”update project translation memory” at the end? Is there a way I can choose to include only certain segments? And also, the other way round, to include the whole document minus certain segments (references etc.)?