The View Headers Toggle Button extension does not work for me in TB 1.5
but FYI, there is a functionally similar extension available that does
work: _Headers Toggle_ :

Simply press the "H" key on your keyboard and headers will go from
"Normal" to "All". Press "H" again and they will return to normal.

I tried modifying the install.rdf file for View Headers but had no
success (and emailed the author as well).