The builder is mostly mouse-driven — you drag blocks in, click to select, and edit in the panel on the side. There are a handful of keyboard shortcuts, and this is the honest, complete list. On a Mac they use Command; on Windows and Linux they use Control. The builder figures out which one you're on.
These work while you're editing a page or post. Undo steps back through your changes; redo puts them back.
When your cursor is inside a text block, these format the words you've selected:
There's no shortcut for saving, deleting a block, or duplicating one — those are buttons and menus in the builder, not key combos. If a shortcut isn't on this page, it doesn't exist yet. When more get added, they'll show up here.
No. Saving is a button in the builder, not a key combo. The shortcuts that exist are undo, redo, and text formatting.
Yes. On Windows and Linux, use Control where a Mac would use Command. The builder detects your platform.
You don't — there's no delete shortcut. Select the block and use its controls in the builder.