I have a question in regards to the key definitions again...
First, operation of the function keys, due to improvements in .xbindkeysrc are quite good. But, now some of my previous defintions involving Mod5 do not work. For example to obtain
the left bracket, {, I had used

"xvkbd -xsendevent -text '{'"
Mod5 + Left

Now the result of typing of Mod5 + Left just behaves as if I had not pressed the function key.

Any clue how to get this type of definition to work again?

Also, I happen to notice that keysym.h and keysymdef.h
are not located as described in the comments in .xbindkeysrc