After adding long text, it cannot be saved when modifying.

First of all when you want to post large text. in storage you should set text type to large (default is normal). You can check your PHP memory size.
Check dev version it fixed value when using WYSIWYG

Field: text
Storage :big
Widget: text_format

As long as the text_format is selected, the rows setting is not displayed, the default format setting is not displayed, and the field cannot be saved when it is modified.

I cannot reproduce your problem. it works fine on my environment. Try dev version with fresh drupal 10.2.5 and see if it work.

To reproduce the above error, freshly install Drupal 10.2.5, node add article type, add long text for datafield,
Field: text
Storage :big
Widget: text_format

The above error is reproduced, and there is no response after clicking Save.

I think your theme has a problem. i test on theme bootstrap 5 admin → , claro, gin → . i don't get any error at all. I think your theme is not displaying the class correctly for many fields

The error is not reported on the page where the content is added, but when a field is added to the content type and saved, an error will be reported when the field is set again, or when an existing field is reused in another type.
For example, if you click Re-use an existing field, select datafield, enter the field setting interface, and click Save to get an error.

Only when you use text_format will the error be reported, and if you use textarea, no error will be reported.

An error occurred in the following path,
/admin/structure/types/manage/article/fields/node.article.field_abc

After testing, it was found that the problem was not fixed, and the setting default value was not enabled in the setting field, and the problem still existed, and the message An invalid form control with name='default_value_input[field_abc][0][value][format]' is not focusable, when setting the default value is enabled and Text is selected Format, you can perform a save, but the text format is not saved to the database.

You can't save multiple values in a data field, that's for sure. If you want a text field with full formatting, data field is not an option or use a paragraph

Automatically closed - issue fixed for 2 weeks with no activity.