When using custom filter, I have the following code:

accession is defined AND accession ne '';
subj_id is defined AND subj_id ne '';

I received the following error message:
line 2, Statement doesn't appear to do anything.  (I am not sure why line 2 did not do anything)

But if the code is written this way, then it would be okay.
(accession is defined AND accession ne '')AND (subj_id is defined AND subj_id ne '');

My question is, does custom filter only allow one line of code?

I will appreciate any input!