Greetings,
I want to add additional photos to an existing gallery and from what I can tell this option doesn't exist. I go to my gallery block, hit edit. In here, one will notice several options. Content, Design at the top and Upload Media and Use Existing Gallery as selections.
When I click Upload Media, one has two options. Either click Upload Images or click the plus (+) sign in the bottom right hand corner (which allows you to search through already uploaded images - which is helpful).
When I click search, one has the three options above. Free, Premium and Imported.
I click Importe