I did try that, but my diffs tend to be those against the repository, not a second file (other than the temporary file created by SE to pass to diffzilla). Thus, I go to Tools -> Version Control -> Diff...., this doesn't ever provide a dialogue to configure lines, but goes straight to diffzilla.
I just tried taking a file I'm working on, purposefully moving a method from one location of the file to another and then arbitrarily removing a line of code. Saved and then tried Tools -> Version Control -> Find symbol changes in <file>... Selected the method I moved and afterwards it stated there were no changes (yet I removed a line of code, so there was a change). Where Tools -> Version Control -> Diff <file> with most up to date version showed the block addition and block removal).
As stated before, the pull downs in the latter SE launched diffzilla don't seem to do anything other than relocate placement in the corresponding file/buffer (Select the method in the first window places the cursor to the method with second window showing the deletion block, but set the pull down in the second window and it just relocates the cursor to the method in the second window, shift the first window with it to its deletion block).
I look forward to the new feature, which hopefully handles this use case. Or, some how when SE launches diffzilla indirectly via version control, it provides the missing dialogue box so that you can check the specific lines, et al.