drupal 8 display block in view footer/header

Question

in drupal 8 core views, in any view you can add header or footer field with "Rendered entity - Custom block". When you do so, it asks for the block id, which appearently is machine name of the block.
A search form block has an id equal to bartik_search and that will make the search box to display. But i have my own custom block created and it has Machine name: modallink and i want it to display instead.
Problem is, when i enter modallink into the "block id" box, it doesn't work. Nothing gets rendered.

What is ID of my custom modallink block?
Am I using the "Rendered entity - Custom block" field incorrectly?

Answer 1

It's horrible, but here is what seems to work:

• Go to structure -> block layout
• place your block in random area of your theme
• go to the page settings and hide the block on all pages but some invalid url (for example enter 'none'
• go to your view, place the block in header / footer
• click the checkbox for 'bypass access checks' in the setting-popup.