At any time, you can test a CustomBlock definition without exiting the Block Editor.
The CBTestBlock command displays the current Block definition in a test window.
You can make changes to the CustomBlock definition and test the effect without saving the CustomBlock definition.
The test window closes automatically when you close the Block Editor. Alternatively, use the CBTestClose command to close only the test window.
It is recommended to test the CustomBlock after each modification to prevent errors.
To test a CustomBlock:
The corresponding Block reference appears in a test window.
To close the test window:
Access
Command: CBTestBlock
Ribbon: Edit Block > Save > Test Block