[META] [UX] Add more Display Suite features

Changes we'd like to see in Backdrop Core: * [x] Add blocks for individual fields * [x] ability to create custom display modes * [ ] #1691 - create reusable set of blocks * [ ] #2894 replace the Manage display page with something similar to the Layout UI

Features that may not meet the 80% use-case requirement: * [ ] Field groups module in core * [ ] Add a "manage form" page separate from "manage fields" * [ ] Override the display label text (separate from the form label text) * [ ] Control the HTML output of fields, (Fences module, Field Wrappers module), see https://github.com/backdrop/backdrop-issues/issues/2608#issuecomment-504... * [ ] Set classes on field level elements (Fences module), see https://github.com/backdrop/backdrop-issues/issues/2994#issuecomment-370...

Related issues: * [ ] #4341 Allow 'Main Page Content' block to use a specific display mode

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Original issue:

I'm considering to build new websites for some of my clients with Backdrop instead of Drupal. As I use Display Suite a lot, I'm wondering if the module could be ported or if some of it's functionalities could be integrated into Backdrop core.

In my opinion, the main concept of Display Suite, i.e. the ability to arrange node displays (and other stuff) without touching template files, would fit perfectly the statement "Backdrop values site builders over coders". Reading layout related issues like #933 #774 or #1100 I got the impression that Backdrop members have reservations regarding Display Suite, which however might not be related to the mentioned Display Suite main concept but to other aspects of the Drupal module.

As I'm not able to code, I'd like to start a discussion if it makes sense to port some of the Display suite functionalities to Backdrop. Are there other (former) Drupal site builders who miss Display Suite in Backdrop? And as there are layouts in Backdrop, which Display suite features do you miss anyway?

One example: In #1100, @docwilmot stated that a meanwhile existing Backdrop feature (Adding blocks for adding individual fields from entities) "would replicate the functionality of Display Suite in Drupal: the ability to have fields from a node (or an entity) placed anywhere in a layout". The "adding field blocks" feature is a nice addition, but in my opinion the manage layout page shouldn't be the standard place to manipulate the display of nodes, and single blocks are not the ideal context to show node fields.

In summary, I'd like to manage the field display of nodes (or other entities) on the manage display pages, but the options are to less. Currently you can reorder fields there, hide or place the field labels and choose a format. I'd like to do some more stuff, e.g. change the name of the label, change the HTML output of the field, and some more stuff which coders might change in template files. What do you think about it?