Pasting the list of keyboard shortcuts from the bubble editor for better visibility and search engine indexing.
I also wanted to include a handy keyboard shortcut reference app I built for myself. This will create a slim popup that you can ‘dock’ to the right of your editor while learning the keys.
App: Keyboard Shortcut Quick Reference Sheet
These keyboard shortcuts are likely to be a very valuable timesaving tool for people in this forum. 
Ctrl+P
Preview your app, equivalent to clicking on PREVIEW
Ctrl+T
Switch between the Design, Workflow and Data tabs
CMD + Click
Select the element under the current element
CMD + Drag
Resize the current element symetrically
Shift + Drag
Resize and keep proportions constant
Ctrl+C
Copy current element, action or event
Ctrl+V
Paste current element, action or event
Ctrl+X
Cut current element, action or event
Ctrl+Shift+C
Copy current element’s formatting
Ctrl+Shift+V
Paste formatting to current element
Ctrl+D
Duplicate current element
Ctrl+K
Show/Edit workflow for the current element
Ctrl+A
Select all elements on the page
Ctrl+G
Group the selected elements and move them in a new group
Ctrl+E
Center current element relatively to the parent
Ctrl+B
Turn this text element bold
Ctrl+I
Turn this text element italic
Ctrl+U
Turn this text element underlined