If your form is decomposed in parts, you can create differents bricks in the same layout.
It will create different sub-template files and you will be able to create easily some tabs.
BUT :
In your case, I think the best is to create 2 form layouts.
In the builder, Create a second template with a form brick inside.
Then, anywhere you want you can call the page for editing this extended form in popup.
For example in the grid :
Choose a column and from the column properties, create a link to your second form layout. Then also specify 'modal'.
This is not possible to 'link to layout' on special fields of tasks. Try on a simple string.
Hope it helps.
