Modify keyboard

First, export your keyboard configurations to a file:

$ xkbcomp -xkb $DISPLAY xkbmap

Modify file xkbmap.

Save and reload keyboard configurations:

$ xkbcomp -w 0 xkbmap $DISPLAY

So far no root access is required.

   key <AC01> {
       type= "FOUR_LEVEL_ALPHABETIC",
       symbols[Group1]= [               a,               A,           braceleft,              AE ]
   };
   key <AC02> {
       type= "FOUR_LEVEL_SEMIALPHABETIC",
       symbols[Group1]= [               s,               S,           bracketleft,           U1E9E ]
   };
   key <AC03> {
       type= "FOUR_LEVEL_ALPHABETIC",
       symbols[Group1]= [               d,               D,           bracketright,             ETH ]
   };
   key <AC04> {
       type= "FOUR_LEVEL_SEMIALPHABETIC",
       symbols[Group1]= [               f,               F,           braceright,     ordfeminine ]
   };
   key <AC05> {
       type= "FOUR_LEVEL_ALPHABETIC",
       symbols[Group1]= [               g,               G,           backslash,             ENG ]
   };