If you'd like to bulk edit planned dates, time estimates, frogs, rewards, or if you'd like to do the standard bulk operations using your keyboard, then do the following.
First, bulk select the items you'd like to edit by clicking one item and shift clicking another, or by ctrl/cmd clicking one or more items.
Then, type one of Marvin's keyboard input shortcuts to start autocompleting. When you press tab or enter to autocomplete, the selected tasks/projects will be edited in bulk.
For a full list of task input shortcuts, see this article: https://help.amazingmarvin.com/en/articles/1949399-using-shortcuts-while-creating-a-task
Note: some shortcuts like "load" don't work when bulk editing tasks/projects.