Here is the solution that resolved the issue:
In order to regain access to the JSDT JavaScript editor, it is necessary to first uninstall Eclipse Wild Web Developer and then install JavaScript Development Tools from the Eclipse IDE 2020-03 version.
Uninstalling Eclipse Wild Web Developer: Navigate to Help > About Eclipse IDE: Installation Details, go to the Installed Software tab, select Eclipse Wild Web Developer, and click on Uninstall
Installing JavaScript Development Tools from the 2020-03 version: Go to Help > Install New Software..., use this link , and choose JavaScript Development Tools for installation