I tried to use the batch conversion, but there is no batch conversion under "tools". I can only export files, that's all and only one file at a time and not all together.
I'm using:
XnView QT
Version 0.12 (Nov 19 2008) Libformat version 5.06
no batch conversion
You are using XnView MP which is under development and which hasn't got the Batch functionality, yet. You have to use XnView Windows or XnView for Un*x. (Not 100% sure that XnView Un*x does support it).