From the Explanatory Notes of EASA List of Class or Type Ratings:
Before operating the aircraft detailed in the respective Licence Endorsement Lists, it is
the responsibility of the competent Authority to ensure satisfactory assessment of
such aircraft.
2.4 FCL.710 addresses class and type ratings concerning variants. In order to
extend his/her privileges to another variant of aircraft within one class or type
rating, the pilot shall undertake differences or familiarisation training. In the case
of variants within a type rating, the differences or familiarisation training shall
include the relevant elements defined in the operational suitability data established
in accordance with Part-21.
Differences training requires the acquisition of additional knowledge and training on
an appropriate training device or the aircraft. Familiarisation training requires the
acquisition of additional knowledge (GM1 FCL.710)
Whenever “(D)” is indicated in column 3 in one of the lists mentioned in
paragraphs 2.1 to 2.3 above, it indicates that differences training in accordance
with FCL.710 is required when moving between variants or other types of aircraft
which are separated by the use of a line, in column 2.
Although the licence endorsement (in column 4) contains all aircraft listed in column
2, the required familiarization or differences training must be completed before
operating the respective variants