Your issue is with the 'TeX Text' which uses its own pygtk window. You might consider reporting this to the 'TeX Text' issue tracker <http://bitbucket.org/pv/textext/issues/>.
Proposing to close as 'Invalid' -> upstream issue in 'TeX Text'
Besides that - none of the native Inkscape extension dialogs have an Undo function either (Inkscape 0.46+devel r22200 on OS X 10.5.8).
Your issue is with the 'TeX Text' which uses its own pygtk window. You might consider reporting this to the 'TeX Text' issue tracker <http:// bitbucket. org/pv/ textext/ issues/>.
Proposing to close as 'Invalid' -> upstream issue in 'TeX Text'
Besides that - none of the native Inkscape extension dialogs have an Undo function either (Inkscape 0.46+devel r22200 on OS X 10.5.8).