If a temporary tablespace is not the default temporary tablespace for the whole Database, it is possible to drop it from ONLINE mode directly. If it is a default temporary tablespace, it is not possible to make any changes.
Toad allows you to try and bring a temporary tablespace offline in OFFLINE mode.
The 'Take OffLine' button should be grayed out in Toad, however it is still active.
If this button is clicked, the following error appears: 'ORA-03217: invalid option for alter of TEMPORARY TABLESPACE'
Enhancement request ST 63955 has been submitted to Development for consideration in future release of Toad for Oracle