Learn more about the ESC here: https://wiki.documentfoundation.org/Development/ESC
LibreOffice was already capable of filling forms via form controls or form
fields. OOXML gained a third way of filling forms: content controls in 2007.
The feature set provided by content controls is not something Writer could
fully represent, so the way forms are created by default in Word resulted in
formatting loss during handling of them in Writer. To solve this problem,
native content control support was added to Writer, inline content controls as
a start. Come and see how this work is implemented, where are the still rough
edges and how you can help.
ESC call, a conference edition.