Iterable allows you to clone blast and triggered campaigns. To clone a campaign, hover over a campaign and click 'Clone'.
For blast campaigns, this will create a clone of the campaign but will not schedule the campaign. The cloned campaign will use the same list and template as the original campaign.
If the original campaign had an unfinished A/B experiment associated with it (if there is still an option to "End Experiment"), then that experiment will also be cloned for the new campaign. If the original campaign's experiment completed with a winning variant (denoted by a icon), then that variant will be used for the cloned campaign. If there was no winner selected, then the control will be used for the cloned campaign.
You will be able to make template design changed before you schedule the new campaign for send.