First may I add my voice to those many other who are grateful for being here ... a big thank you.
I like the new collections system particularly the ability to specifically add or exclude resources to a search criteria.
The screen says 'drop resources or collections to add here'. i.e. Nested collections YEAH! 
but ... How do you drop a collection?
I can drag a resource from the library window but collections do not show up as resources, and I can only open one collections tab at a time so cannot drag from collection to collection.
BTW. Is there a way to search only this forum before posting rather than the whole site?
