You can select custom models and glossaries in the Plugin configuration form. The described settings are available when the selected provider supports them. For some providers, you can choose from the list of possible models, for other ones you'll need to enter the full name of the model and/or glossary.
Since models and glossaries are usually configured for a specific language pair, you need to specify the language pair when saving such settings. We'll test the settings a small request for this language pair:
If the verification is not successful, we recommend you to verify the correctness of the selected provider, model, glossary and language pair.
You can keep the settings if you are sure that they are correct.