Secrets of the User Interface (Hotbar, To-Do List, and the MYSTERIOUS RADIAL MENU)

Basically this is a list of things and instructions on stuff that's not explicitly stated by the developers NOR the game itself.
I haven't seen any other guide talk about it either.
I'll update this later on, I just need to get this text out there.
EDIT-Updated with screenshots, will add more context and clean up throughout the week.
Also realized I was wrong on a few things, will dive a bit more deeply on how this works.
EDIT-Adding Misc Tips and Knowledge. 1k+ hours on this game and they never once mentioned certain things in the section.
EDIT-11/26/24-UPDATED, I noticed something out of the corner of my eye while in the radial menu. The UI in this game drives me nuts sometimes lol.

The Basics

I know a lot of people know about Alt-Scroll wheel for swapping between hotbars and some other basic things here and there, I'm just listing it out for those who don't know.
I don't know why Coffeestain didn't make certain things explicit, but here it is:

The To-Do list, while buggy, can be accessed without needing to set an item on it

1. Press TAB to open the inventory.
   
2. Move mouse to the right edge of the screen, centered horizontally.
   
   
3. A vignette/shade effect should appear-That's the way to access the To-Do List.
   
   
4. Behold, the list-Seriously, the UI needs a tutorial or something. I don't think they included this in the new/updated onboarding process.
   URGENT-Use the X button in the corner to leave the To-Do list. Something bugged out on my end, hitting esc or clicking outside of it inconsistently saved the contents of the list. I'm not sure if this affects all copies of the game or if it's just me.
   In addition to that, the [?] In the left-side corner of the windows of the list provides formatting for bolding lettering, and creating checklist boxes.
   

The Hotbar on the bottom, likewise has some interesting features I didn't know about. I know this seems obvious, but I'm more pointing out the "unassigning" and the fact you can assign pretty much anything to the hotbar.
NOTE: The word ELEMENT in this context refers to buildings, patterns, color swatches, AND blueprints.

1. Open the Build Menu with B.
   
2. To assign an element to a key, hover the mouse over an element and then press the corresponding key.
   
   
3. To clear a hotbar slot, either hover over the corresponding element and press the corresponding key it is linked to.
   
   
4. Alternatively, hover over another unrelated element and simply mash down twice on the numbered slot to clear it. (Assign, unassign)

While the above IS "explained" at the bottom of the menu saying "Bind to Hotbar/Hover + 0-9", this is just an expanded explanation because it doesn't clearly state how to clear the hotbar.

A Bit More on the Hotbar and Radial Menus

This is where things get kinda interesting.

1. When building, customizing, or placing blueprints, the UI indicates the [E] key can be used to "Quick Switch" between different elements.
   
2. Constructor swaps to Assembler, Conveyor Belts swap between different versions of themselves, so on and so forth.
   
3. Foundations, Color Swatches, and Blueprints are subject to this effect, but it's kinda muddled-The element you assign is either in the same or similar category, as Quickswitching by lightly tapping [E] cycles through 1-4m variations of the basic flat Foundation-but holding down [E] lets you access much more through a radial wheel-
   
4. With that said, hold DOWN the [E] key to open a radial menu to a subcategory or multiple subcategories depending on the element assigned to the hotbar slot.
   
   
   
   
   
5. Blueprints DO appear in the radial menu, but ONLY in the subcategory YOU assign them to. Custom elements in the radial menu, such as blueprints cap out at 12 before another PAGE is made. Yeah, that's right, there's layers to this. Holding down the [E] key and [Left Mouse Click] or [Right Mouse Click] cycles through pages of subcategories that extend past 12 or more elements. The two pictures below show what I'm talking about. Look at the edges of the screen where it says "NEXT" [LMB] and "PREVIOUS" [RMB].
   
   Assigned 50 blueprints to one subcategory because you were lazy? Enjoy the massive menu. It won't work-Maximum of 12 blueprints fit on the radial menu before it bugs out and doesn't show it. And I repeat, they also Quick Switch/Cycle through said assigned subcategory.
   
   

• Holding down [R] lets you access the radial menu of build modes with Foundations and similar constructs.
  
  
• When using the radial menu for foundations, look at the right and left middle sections of the edges of the screen- You'll see [PREVIOUS MATERIAL] on the left and [NEXT MATERIAL]
  True to what it says, it can be missed if you're focused on the center of the screen 90% of the time (what is going on with the UI in this game?).
  
  As you've seen in the screen shots, I have anywhere from 4-7 buttons max on the hotbar to access a LARGE majority of Foundations, Architectural Buidlables, and Patterns for quick base creation-
  So the above means I can have 5 different subcategories to access on my left hand making building much less of a chore.

A Few More Details

Meant to include this but forgot.

• The metal beams/painted beams have alternate connection forms when you Quick Switch or click/hold [R].
  
  
• Diagonal lets you move the beams around at, well, diagonal angles.
  
  
• Freeform means you can make the beam attach to a joint, but not a beam mount(don't ask me why, ask Coffeestain) at any angle.
  
  
• There's a dude on reddit who essentially uses beams to make custom machines/designs.

Some more random facts-

• Holding [CTRL] when building can replace similar objects, i.e. replace a normal wall with a conveyor hole wall, and swapping splitters around. Note objects WILL keep their rotation-it seems you must replace buildables to rotate them. Got this tip when watching a stream.
  
• Back to blueprints-BLUEPRINT YOUR SIGNS/PROGRAMMABLE SPLITTERS/SMART SPLITTERS GOOD GOD I SHOULDA BEEN DOING THIS WAAAY BEFOREHAND

Misc. Tips and Details

Stuff that doesn't really have a place in the guide, but is NOT explained in the game period.
Will add more as I scour the net.

• Hidden Powerpole Tech
  
• When setting up manifolds, place the belts first in front and behind your machines, then snap the splitters/mergers to the belts last. Much faster imo to setup than trying to measure each splitter/merger out.

[Faflis]

The search menu can be used as calculator.

[GoldCoekie]

Thanks, this realy helpt.