The most helpful hints I could find were here and here.
Following this advice, I edited my
~/.vmware/config
file to look like this:xkeymap.nokeycodeMap = true
xkeymap.keysym.ISO_Level3_Shift = 0x138
xkeymap.keysym.braceleft = 0x1a
xkeymap.keysym.braceright = 0x1b
I think the second line is the most important for my German keyboard, as it maps the AltGr key.