There are number of FHIR Questionnaire Builder packages. Some of the most popular packages are:
Structor
This is an open-source tool that allows you to create FHIR Questionnaires from scratch or by importing existing ones. It also includes a live demo that you can use to test your Questionnaires.
Github: https://github.com/helsenorge/structor
Demo: formdesigner.helsenorgelab.no/
Language: React
Developer: Helse norgeLHC FHIR Tools:
This is a suite of tools that includes a Questionnaire Builder, a Questionnaire Viewer, and a Form Builder. It also includes a SMART on FHIR app that you can use to fill out Questionnaires.
Github: https://github.com/lhncbc-fhir/lforms
Demo: https://lhcformbuilder.nlm.nih.gov/previous/
Language: Angular
Developer: NLM/LHNCBCForms Lab
This suite provides various tools to build the Questionnaire, complete the form and also map the Questionnaire with other resources.
Demo: forms-lab