Right now, able to create a lien waiver in QuickBooks Online (QBO) is unavailable. You may wish to consider looking for a third-party app as QuickBooks integrates with hundreds of third-party software developers.
I can route you to the website to look for an application specific to your business needs. From there, you can integrate the app to QBO. To view a wide range of options, use specific keywords to narrow down the search. You can check the reviews from other customers to help you decide which app suits your business type and needs.
Additionally, to know how the contractor works in QBO, see the below articles: