Hi @takafumiohtake.
The only thing that you need to do is bump the @forge/ui version of the package to 1.2.0 version and redeploy the app. It should result in displaying the custom field edit entry point directly inside the create issue modal instead of showing it in modal after clicking on it.
For issue view the behaviour stays the same and there are no difference for it.
Yes, the same function will be called for issue view and create issue dialog, but for create issue dialog it will behave a little bit differently.