Tested with the Portuguese speller only so far:
Using LibreOffice 6.2 beta 1, the words which are in the speller but which don’t have morphologic information appear underlined in blue.
When we right-click on them it says they are unidentified.
Could the underline have a different colour, such as pink?
This would help in the task of adding all the unidentified words to the added.txt .