form submitted value as token I have created a form by extending FormBase class. In form, I'm having a field called "name" where user can input his name. While submitting form, I want that submitted name convert into token so that I can use that token sending emails.

example.com/admin/config/people/accounts, here is the Drupal default configuration email forms.

What I want is to use custom form field value to be appear as a token inside drupal default email config forms.How can this be achieved?

Any help is appreciated. Thanks.
Tokens are just a representation of some other data structure that exists.

You can not convert an arbitrary value into a token. What you need to do is store the value and then define a token for that stored value using hook_token_info()/hook_tokens().

I understand it's a per-user value, so the simplest option seems to define a field on the user entity, I don't quite understand why you don't just show that in the profile. Then you can easily access it as a token when using the token module.