After updating from D9 to D10, the ability to choose the text editor format disappeared in all forms.

Did you export your configuration after updating the webform module?

Thank you very much for help,
I compared the files and it turned out that during the conversion from CKE4 to CKE5 I removed the full HTML format (CKE4) too early and switched to CKE5. The option to select an editor has disappeared.
After restoring the full HTML format (CKE4), you can go to the settings again.

Conclusion: First, you need to set the HTML editor settings to CKE5 in Webform (/admin/structure/webform/config/elements) and only then you can safely delete the CKE4 editor profile.

Maybe my mistake will be useful to someone who, like me, is in a hurry to delete the old CKE4 profile.
Now everything works properly.

Best Regards

Actually it should be this status.