Electrical – Custom Libraries in Altium not showing components

1) Open the "SCH Library" panel:

2) Add a new part(s) to your libaray:

Now there are two different parts ("Part A" and "Part B") listed under your components name:

Each of them has a different design screen. Click on the one you want to design. Design the two parts separately.

3) Assign which pin belongs to which part:

Notice that the pins 4 and 8 belong to both parts and always active. Pins 1, 2 and 3 are only active when Part A is selected. Pins 5, 6 and 7 are active only when Part B is selected. The pins of the non-selected part are always grayed out.

If the some of the pins do not match to their corresponding parts, alter the settings in the "Component Pin Editor" dialog box.

Change the pin order to state which pin belongs to which part.
1: Part A
2: Part B

That's all. Now we have two separate parts in one component library.

Making the footprint is generally one of the fastest of all the things you need to do. There are Wizards in Altium that help you make IPC-compliant footprints quickly, and you can set the text height, silk screen line widths and so on to conform to your specific requirements and so your boards have a consistent appearance and set of manufacturing requirements.

Populating the data base with all the things that should be there (vendors, part numbers, alternates, prices, and so on) takes longer. Making a 3D body, if you need to, can take a lot longer depending on your proficiency with 3D parametric modelling software and whether you want to do a good job, a spectacularly good job, or something more slapdash. Here's a rendering of an LED body I did some time ago- the actual die dimensions and position is shown but I didn't bother with the bond wire. The typical library parts often have a crude 3D block or nothing at all.

You only make the part once and you can re-use it thereafter. It's a big hassle to add parts to inventory for the rest of the company, so maybe it will make you think twice about reuse.

Anyway, if you're at the beginner stage (we've all been there) and you just want to get going, use an 0805 resistor and it will be sub-optimal but usable (ignoring the 3D features and such like). You can edit it to show the polarity and save it in a library of your own. You can also download someone else's library that's been done more-or-less properly and (hopefully) learn from that and create your own as you gain experience. IIRC, the 0805 and other Imperial standard footprints may use the metric equivalent numbers (2012 for 0805) as part of their names.