Tricky because the class assigned to a paragraph tag may be different between books
Maybe this will work for your (simple) text files
Pre process before attempting the merge
I will assume you have a WIP library (work in progress)
1)add the
TXT file to the Library
2)
convert to EPUB
3) now using the editor, bulk change the class= to the new selector
NOTE this name may be in use other places SO YOUR PREVIEW MAY LOOK OFF
Save (just in case)
simplest, if small)
Copy all to Clipboard
Now switch the editor to the destination book (
previously
edit the book, so it will be listed in the file history)
4) Create a (temporary) New (blank) File in the book.
5) paste the clipboard into the blank file, remember to link the stylesheet if you want to preview
6)Move the text to its home as desired
That should do it