★How to change text height for text within the block

Issue:

How to change the text height for text within the block without entering the block editor?

Solution:

Find Express from the menu, then expand Blocks, and select Change Block's Textheight (command: CHGBHEI). Select the block and set the new value for the text height.
All the texts including the TEXT and MTEXT objects within the block will use the new text height.