Overriding Flexform example is wrong: uses extension key with underscore in "plugin signature" about typo3cms-reference-tsconfig HOT 1 CLOSED

I looked at this some more, in the description

Other properties also apply to flex form fields, in this case the full property path including the data structure key has to be set: TCEFORM.[tableName].[fieldName].[dataStructureKey].[flexSheet].[flexFieldName].[propertyName]. The [dataStructureKey] represents the key of a FlexForm in $GLOBALS['TCA'][]['columns'][]['config']['ds']. This key will be split into up to two parts.
By default the first part will be used as identifier of the FlexForm in TSconfig.
The second part will override the identifier if it is not empty, list or *.
For example the identifier of the key my_ext_pi1,list will be my_ext_pi1 and of the key *,my_CType it will be my_CType.
https://docs.typo3.org/m/typo3/reference-tsconfig/main/en-us/PageTsconfig/TceForm.html#additems

So, we can look in $GLOBALS['TCA'][<tableName>]['columns'][<field>]['config']['ds'] for the key, but from what I checked it should be myext_pi1, not my_ext_pi1.

Test with sf_register and TYPO3 v12:

TCA: tt_content.columns.pi_flexform.config.ds:

sfregister_create,list = FILE:EXT:sf_register/Configuration/FlexForms/create.xml

has no underscore in extkey (sfregister instead of sf_register_create).

Page TSconfig works without the underscore:

# is added to list
TCEFORM.tt_content.pi_flexform.sfregister_create.sDEF.settings\.fields\.selected.addItems.ZZZ = ZZZ
TCEFORM.tt_content.pi_flexform.sfregister_create.sDEF.settings\.fields\.selected.addItems.AAA = AAA


```![image](https://github.com/TYPO3-Documentation/TYPO3CMS-Reference-TSconfig/assets/13206455/fafaabda-6afa-406d-a9dc-435c3b6c330a)

from typo3cms-reference-tsconfig.