A heading can have an unsorted part. The unsorted heading part serves to include in the heading certain linguistic information which helps to understand how to use the heading word (what words the heading is usually used with, government model examples etc.) yet, if it were sorted, affects the heading position in the word list in an undesirable way.
The unsorted heading part is not displayed in the word list, doesn't affect the word order in the word list, isn't used when comparing words. The meaning of all this is that when you add an unsorted part to a heading you don't create a new heading, and so you can't use tilde to denote both the heading and the unsorted part you added.
The unsorted heading part is displayed only on an open card. You should use braces to select a part of the dictionary text as the unsorted part of a heading. See the following example on the use of the unsorted heading part: