1. How can I set the prompt in the files section ?

Use the `fileprom' static file parameter.  Try `fileprom : [$f] :'
as an example.  (it was undocumented before v1.65)

2. I use a Fossil driver and a 16550 UART with FIFOs enabled. After
     someone transfers a file, why does it seem as if characters are not
     being transmitted?

If you use DSZ, it directly accesses the UART, and uses the
FIFOs.  By default, it turns them OFF when it finishes. Since
Waffle doesn't reset the Fossil driver, it tries stuffing
characters into a buffer that's turned off.

The fix is to use the `F' flag on DSZ's command line in
/waffle/extern/_send and _receive:

Z /command="C:\waffle\bin\dsz F port %d est 0 %b sz -m %i",

or to use the new (as of 1.65) /reset flag on the extern to 
make Waffle reset the FOSSIL:

Z /command="C:\waffle\bin\dsz port %d est 0 %b sz -m %i" /reset

This can also affect file transfers using the built-in
editor.

3. People with priv 9 can access the file section fine, but people with
    normal access get `Validation is required to use the FILES section.'

Check your /waffle/system/dirs file.  This error occurs if
the user does not have access to the root file directory
(`files:' in the static file).  A sample from hogbbs's (working)
configuration:

        /waffle/system/static:

                files: f:/file

        /waffle/system/dirs:

                1 /dir="f:/file" /access=1