This method is useful if, for any reason, you should find your current TiddlyWiki instance is not saving (e.g. a plugin or a server has stopped working). It should work on just about any platform.
Go to advanced search
Goto the filter tab
Enter the following filter text:
Check the list of tiddlers.
Adjust the number "25" in the filter to make sure you found all your recently modified tiddlers
Press the bucket with the up arrow  which appears on the right
A dialogue window will ask for a location to download a file called tiddler.json on your local drive, or depending on browser configuration, just alert you that such a file will be downloaded. Press save.
The tiddlers.json file can be imported (tools in sidebar) or drag and drop the file on the top line of the story river of another TW .