For a certain schema, Object Explorer shows words "Toad for Data Analysts" under Views node of objects tree. There are no view names listed here. If mouse is hovered over "Toad for Data Analysts", the "ORA-00936: missing expression" error is shown.
Custom SQL filter is entered for Views node.
Clear out all filters using the Filter ( Funnel) icon of Object Explorer. If issue persists, use Filter icon to open Filter window and select SQL tab to remove entered SQL code.