Combining TMX files
To combine several TMX files, place them in a folder. Then open the folder via Memory > Open memory … Choose Memory > Save memory and assign a name to the merged TMX file.
If you want to merge an individual TMX file with a TMX file that's already loaded, choose Memory > Merge memories … Browse for an existing translation memory file, and merge its content into the currently-selected translation memory in the tabbed pane.