Mass adding tasks to projects already created

Hello 🙂

This may be a little niche, so apologies if no one else has come across a need for this...

We have projects that are built from a series of blueprints (currently 70 active) that reference each event. However I want to make a change/ add a series of extra tasks to these blueprints but I can't seem to find a way to "roll out" the changes to all active projects that have come from the blueprints. Is this possible or can anyone suggest a work around save manually adding tasks 70 times.

Many thanks, 

Kyle