Yes what you ask is possible,
Drag and drop any text file to a TiddlyWiki and it becomes a tiddler. Or use the Import PageView Icon
Even json files and others as long as the content is not binary.
The title will be set to the filename, and you may then want to annotate, rename, tag etc.. in tiddlywiki.
If you construct correctly formatted tid files you could import/drag and drop those with the desired titles, fields and Tags.
Export a tid file and edit it to see
Regards
Tony