How can I create a guided navigation tour with LiveView?

In Phoenix liveview, how can I implement step-by-step tour that open modals/tooltips to walk users through different sections of a page in my site?

Sounds like a job for Javascript. Some open source libraries to look at are Tour Guide and Shepard. You could configure those to run in a Phoenix Hook and send a step-completed event every time the user finishes a section of onboarding.