Delimited Identifiers must generally be used for database object with names that contain special characters, reserved words or mixed case. Qualifiers are need when referring to an object in a different schema/catalog than the current one. DbVisualizer uses delimited, qualified identifiers in all SQL it automatically executes in response to user interaction, such as when loading the Data tab for a table, dropping a stored procedure or getting metadata for a DDL statement.
For the features where DbVisualizer generates SQL that you can then execute, you can control if you want to use delimited identifiers and/or qualified object names. In the Properties tab for a connection, or in the Tool Properties dialog for a database type under the Database tab, you find the Delimited Identifiers and Qualifiers categories.
In the Delimited Identifiers category you can specify which delimiter characters to use, e.q. double-quotes or square brackets, and for which features to use them: Scripting (all SQL generating features), Auto Completion, and Export.
In the Qualifiers category you can specify for which features to use them, and also if column names should be qualified with the table name in the Query Builder and for Auto Completion.