Toad Data Modeler cannot do an alter script like this at this time. By default, Toad Data Modeler uses temporary tables when generating a Drop and Create statement for change scripts. So, no data is lost. Temporary Table option is set by default in Change Script Wizard.
Example use temporary table:
CREATE TABLE `Entity1_1058177698AF438F9B83E756AD243D40`
(
`Attribute1` Char(20),
`Attribute3` Char(20),
`Attribute2` Char(20)
)
;
INSERT INTO `Entity1_1058177698AF438F9B83E756AD243D40` (`Attribute1`, `Attribute2`) SELECT `Attribute1`, `Attribute2` FROM `Entity1`
;
DROP TABLE `Entity1`
;
ALTER TABLE `Entity1_1058177698AF438F9B83E756AD243D40` RENAME TO `Entity1`
;