[...]
pd-extended 0.43 dont use buttonbar-plugin.tcl.
because there is massage in pd windows:
UNHANDLED ERROR: can't find package base64
    while executing
"package require base64"
    ("uplevel" body line 8)
    invoked from within
"uplevel #0 $tclcode"
FAILED TO LOAD /usr/lib/pd-extended/extra/buttonbar-plugin.tcl
  
 
I think you need tcllib (sudo apt-get installl tcllib).

András