You can handle this by using the Replacement Dictionary Editor to add additional mappings to the bilingual lexicon.
The bilingual lexicon is a mapping of source word-senses to target word-senses. There are no inflectional affixes present in the bilingual lexicon. That's the way FLExTrans builds it. In theory, though, there could be inflectional features or classes present. You can view the bilingual lexicon by double-clicking on the file bilingual.dix in the Output folder or click on the View Bilingual Lexicon button in the Live Rule Tester Tool.
