After a while of learning, I would like to add another field to the note type.
When I do this, all the history data of the cards are lost, which is correct because the note type changes.
However, I suggest setting up an option to save the history data because sometimes it is useful to keep the data of “easy” cards.
At moment, those “easy” cards have to be relearnt, which is not necessary.
I’m relatively sure, from my constant updating of, and tinkering with, my own notetypes; that the review history of cards is not lost upon doing so.
But I’m not certain, so could someone else weigh in?
Yes, it sounded strange to me as well. I’ve made a quick test and history of cards is not lost after note type changes.
Sorry, that’s my mistake!
This is my misunderstanding of the “Templates” table at the bottom of the pop-up window “Change note type”:
There are two columns “Current” and “New”.
I thought I had to select “nothing” in each case so as not to destroy the templates already associated with the new note type by transmitting “old” templates.
Obviously I don`t understand the function of that table.
As a result, I lost the history data. 
Thank you for your time!
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