I am creating a new custom admin page. For reasons I cannot explain here (due to the length of the explanation), I cannot create the custom admin section via Custom Post Type, but rather, I have to create this page manually (and by that I mean, I had to add the side menus and sub menus manually, then add page content manually.... etc.).
Now, I need to create admin "widgets" (I am not sure if this is the correct terminology, but I will explain what I mean by "widgets" in the next paragraphs).
As you can see in the attached screenshot:
One of those widgets is "Categories" (which is circled in red), another is "Publish", and a third is "Format" and so on.
I need the following
What WordPress method/action should I use to add those widgets (example is the "Categories" widget circled in red?
How to make those widgets draggable? (I need to have the flexibility of changing their location)
How do I make those widgets collapsible (e.g., the green circles around the collapse/expand arrows show what I need)
How to add the "Screen Options" drop down (circled in orange)
How to add a screen option for each widget I need to show/hide (example, the "Categories" screen option that is circled in red in the top right of this above image, would show/hide the "Categories" widget that is circled in red)
Important Note: This may seem to be a number of different questions, but I thought those should be asked together, because they are related, I think.
I do not need a full answer, all I need is a pointer to the method, or methods, used for my needs, so I can dig deeper.
I really appreciate your help and cooperation. Cheers.