How to navigate between a few projects

Question

How to open and navigate among multiple projects?

Answer

By Project widget

Use Project widget. Click on the currently open project name in the left top corner of the screen and select a different project to switch to in the dropdown If the project opens in the same window, replacing the currently opened project, change setting "Settings | Appearance & Behavior | System Settings | Project | Open project in… | New Window" ⁠⁠⁠⁠⁠⁠⁠

By tab header (Mac-only)

https://support.jetbrains.com/hc/en-us/articles/40250796588946-How-to-open-projects-as-tabs-in-IntelliJ-IDE-on-Mac-OS