Trying to find where the dictionary(s) are installed under W11. So far searches have not turned up any. I know I have at least one, beause I’ve added words to it.
Try:
C:\Users\USERNAME\AppData\Roaming\LibreOffice\4\user\wordbook
and
C:\Program Files\LibreOffice\share\wordbook
And have a look at:
https://wiki.documentfoundation.org/Videos/LibreOffice_6-4_Installing_under_Windows_10#(Installation)_Custom