Hi, Welcome!

you have 2 options, sort of..

start from the beginning and put all pano's on the droplet again and set all hotspots again.
or

look in the tour.xml
you see scene's
every scene is a pano…
so, what you can also do is..

put only the new pano's on the droplet.
copy the tiles folders in your 'old' tour (in the folder where the other tile folders are swell.)
make sure they have unique names.

then copy the scenes from your new droplet output tour.xml in the 'old' tour.xml.
make sure it works ( maybe copy the new scenes after the old ones..) if not, check the paths /url's to the tiles and thumb and preview etc..

Then you could go adding new hotspots with the editor.

Hope it helps!

Tuur