How to create custom 404 page content

From version 3.6.0 you can create a custom block and assign it to the 404 page to replace its content and edit it with the builder.

1

Create a new block

Navigate to Blocks → Add New and create a new block (you can use any title). Add some content to your liking and save the block.

2

Assign the block as 404 page content

Navigate to Advanced → 404 Page and assign the new created block.

Example: