I recommend using Power Automate now which should not need this setting.
Below kept for reference.
ARCHIVED:
To allow workflow to use add-in permissions
- On the site that you are making the work flow click the settings icon in the upper right corner of the screen and go to Site Settings
- In the Site Actions section, select Manage site features
- Locate the feature called Workflows can use app permissions and click Activate
References:
https://stackoverflow.com/questions/27845480/why-is-app-step-greyed-out-in-sharepoint-designer