Elements 2018

Open the first image then use the menu:

File >> Place

Navigate to, and choose your second photo. It will automatically be placed on a separate layer as a smart object and you can drag to scale and click the green checkmark to commit.

Repeat for the third image.

https://forums.adobe.com/people/j+scotts67032164  wrote Hello - I'm combining three photos into one composite but the copy/paste feature seems to "rasterize" or downscale the image quality.  My research suggest that I want to use the "smart object" of PhotoShop but I'm not sure if this feature is offered in Elements 2018.  Can anyone advise?

If you describe more in detail what you want to achieve to create a composite, you'll certainly get more targetted advice.

Creating a composite from many source media files is a very common task in Elements, especially for scrapbookers or users creating books or collages. You don't need 'smart objects' absolutely, you can get the same quality with normal raster layers and that has always been true even if very old Elements versions.

And it may be extremely misleading to search help from Photoshop specific tutorials. Better ask in a forum dedicated to Elements.

In the present case, while the concept of 'smart objects' is not fully available in Elements, 'smart layers' are available and used in a natural and intuitive way when you drag a photo from the photo bin to your canvas. This shows as a 'smart layer' in the layer pallet, and you have to start from the rectangle preview of the  new layer to decide the location, size and angle of the file on your canvas. Since it's a 'smart' layer, it's not rasterized until you decide so. It always points to a copy of your original source saved into your project. You can change size, position and angle later on, without quality loss, until you decide to 'simplify' (rasterize) the layer. That enables a number of effects only available to raster layers (styles...) and results in a smaller output file in KB.

Note:  the very affordable Elements+ add-on brings back a number of features for smart objects.

About Smart Objects

If I need to transition to a new PhotoShop product to gain the "smart object" feature, which would be the natural upgrade from Elements 2018?  Truthfully I get confused by the product positioning of the many overlapping PhotoShop products (CC vs. LightRoom etc)

Photoshop Elements is  the "consumer" software and it's the only one with a perpetual license. Other tools, considered more 'professional' are available as subscription (monthly or yearly rental). Elements comes with its own organizer and is more oriented towards new users, even if it can satisfy very advanced users.