In the german forum user
WiCk describes how to access the 2nd RAM slot:
https://www.amilo-forum.de/topic,10262,-Tastatur-ausbauen-Amilo-pro-v2040-2-RAM-Modul-u-Tastatur.htmltranslation:
Lift the cover in front of the display where the on/off-button is situated. Use a very flat screw driver or something similar, start on one side and work your way to the other side. Then remove the keyboard (most likely by pushing it towards the display and then lifting it). You'll find the RAM underneath a cover that is fixed with one screw close to the touchpad.
No idea if it really works that way.