Create a views display with a button to add items.
This is an example of combining several modules to create a complete solution with a ton of flexibility.
Implementation
The task list below is a view block with a contextual filter for the referenced project.
It's placed on the project page using layout builder or global block.
When a Project page is loaded, the list shows the related tasks.
Views Add Button module provides a way to add the button to the header.
Since you would want to add a task to the current project, Entity Prepopulate can use a token like [current-page:query:?] to set a default value for the project reference when creating a new task.
You can set up this query parameter in Views Add Button, to set the field value.
To polish further, use Admin Dialogs to launch the create form in a modal.
Example
