[UX] Core's Bulk Operations: Select all items on all pages
This is part of #3797
On a new site, I was plagued with 100's of new dodgy user accounts (because of #574). Because our core's Bulk Operations does not allow me to select all users from the many pages, my options were to either do a direct db query, use phpmyadmin, or manually repeat the process of selecting/deleting/confirming for each of the 12's of pages. This is not good UX, and the 7.x version of VBO included an option to select all items across all pages:

Here's what that option allows:

Yes! I've missed having this in BD too.
...at least we have admin_views in core. I was able to edit the view, change the pager settings to show all items, then was able to select and delete all, then revert the pager settings back to default. Not a viable solution, and can be a performance issue on larger sites; just wanted to put the workaround here for future reference 😉
Putting this here to remember later. We'll have to add functionality to https://github.com/backdrop/backdrop/blob/4426b2be634baa40dab541b2c6a248fe6b1ad6c6/core/modules/views/handlers/views_handler_field_bulk_form.inc. The buttons to choose all or this page is here https://git.drupalcode.org/project/views_bulk_operations/blob/7.x-3.x/js/views_bulk_operations.js#L21. This creates the div to be inserted in the table header: https://git.drupalcode.org/project/views_bulk_operations/blob/7.x-3.x/views_bulk_operations.module#L396. If selecting all it triggers a batch job behind the scenes to gather them all https://git.drupalcode.org/project/views_bulk_operations/blob/7.x-3.x/views_bulk_operations.module#L861 and returns the result to the theme layer to be displayed.
Needs "Feature Request" tag to show up on survey.
I'm going to change the title of this issue, as this refers to core's Bulk Operations, not to be confused with VBO (Views Bulk Operations) which has already been ported to Backdrop and is available as a contrib module.
This issue/request specifically applies to core's Bulk Operations, not the Backdrop contrib Views Bulk Operations. The contrib VBO already has this ability, as @klonos pointed out in the OP.
Just sat watching a colleague delete several hundred nodes, one page at a time for about 20 pages. It would have been so very nice to be able to select all on every page.
This is item 4 on our wish list. https://forum.backdropcms.org/feature-requests
This would make a great feature for 1.33.0. Although there is no PR or an advocate, this ability has a lot of prior implementation in contrib and in Drupal that we can pull from. Marking this as a milestone candidate for better visibility.
@cellear Volunteered during the dev meeting today to be the advocate for this issue. Thank you Luke!