The Variables/Macros dialog lets you view Environment Variables, Built-In Variables, and Macros. This is legacy Tscript technology and here only for support of old projects. Since Tscript is deprecated it is not recommended for use when building projects today.
There is more information on environment variables, built-in variables, local Operator variables and Script variables, and other variable types in the Variables article.
The Environment and Built-in variables are not editable, they are read-only.
Previously Root Variables and Component Variables could be added/edited/deleted using this dialog. To add/edit/delete variables now, go directly to where they are defined which is a Table DAT located at /local/variables of root or the component whose variables you wish to edit.