I think there is no option to "clone" an app in the UI. But you can create a folder app2 and copy all the files and folders from app1 to app2. If app1 has special configuration which mentioned app1 as app configurations then you have to change app1 to app2 in all configuration files like. app.conf OR savedsearch.conf.
Let me know if any further help required.
splunk stopin cmd prompt at
$SPLUNK_HOME$/etc/apps/<app_name>and paste at same location i.e.
$SPLUNK_HOME$/etc/apps/and rename folder name