jmk, My apology. I apparently missed your short answer, “mm”.
I was too focused in trying to find the screen you posted a photo of. I still haven’t found it. Perhaps there have been some revisions in the recent versions. I am presently using V 6.0.07. I need to download the later version, perhaps tonight.
The screen posted is the footprint editor.
The item will show but you will need to extend the RH border to read the description.
I have apologized to jmk. I missed his short, but accurate answer in a longer post. If I offended anyone else, then I offer my apologies to them as well.
I am re-reading the thread and, so far, I do not see that answer anywhere else before your post which I have quoted. I will continue re-reading.
Comprehension of written instructions on specialist internet forums can be difficult.
Assumptions are made, pronouns can confuse, words missed or incorrectly interpreted, different levels of experience, English Second Language translations etc.etc. The list is almost endless. 
Usually everyone finally makes it to the finish line. 
Have you found the “Footprint Editor”?
The second number is the height? What does the height have to do with a footprint? Are the footprints actually 3D models?
I am sorry, but my mind tended to regard any reference to height as being bogus. Perhaps someone can explain that. And if so, can this be seen in the Footprint Editor?
The second number is the height?
yes.
What does the height have to do with a footprint? Are the footprints actually 3D models?
Every footprint has a 3D-model assigned (or at least can have a footprint assigned - some 3D-models are not delivered in the standard lbraries). So if you want a correct 3D-representation from your board the height could be important.
And if so, can this be seen in the Footprint Editor?
in the footprint editor you have 2 options:
With option 2) you have also the ability to assign an own 3D-model, or scale/move/rotate the 3D-model .
To be honest I also mostly ignore the height-value of footprints (and my personal ibraries don’T differentiate between different-height models), but I accept that it’s valuable for others.
So I am reading the library rules and guidelines and it seems that they were violated in the library I was using.
"G1.9 Dimensional Units
When specifying a dimension (e.g. in a footprint name) the units must always be provided:
3mm - millimeters
1in - inches"
Apparently someone did think about this but the author of the library did not get the memo.
Just an observation.
KiCad has the KiCad Library Convention, and it also has some suggestions for filenames.
Library Conventions | KiCad EDA
Library maintainer rules & guidelines
Thanks, good to know.
That option for a bigger, hand solder-able footprint sounds useful. How do I find it? Is it a different library?
Wow! Who would have guessed? Thanks!
Not all footprints are drawn with additional hand-solder-version. (for instance the polarized smd-caps are only delivered with one version).
In the standard-libraries the handsolder-version is placed in the same library as the normal version. Look into the already used Capacitor_SMD library: for simple 1206-ceramic caps you find:
No need to guess… Explore the site.
Explore the site.
Dimensions are shown… Explore the site.
The library is reflecting manufacturers Data Sheets. Height (length) and Diameter are always quoted in those data sheets. Here is just one of dozens of examples.
This thread is getting ridiculous. Learn to use the site and read the documentation and familiarize yourself with the program.
I think it is time to close it.