Can I sort my Steam games by installed size?

Yes. If you go to library and use 'list view' (accessible using the circled button) , then right click in the bar which says Games/Status/Metascore you can select the displayed columns. Click on 'Size on Disk' so that appears as a column, then click on the column header to sort.

If it defaults to showing them in descending order, another click will change the order to ascending.

In the newer version of Steam, go to LIBRARY

and in the second block ("shelf") under "WHAT'S NEW", set dropdown to "ALL" and "SORT BY" "Size on Disk".

Another way to get your games lined up by size on Windows which I adapted from here, and is a little technical, is thus:

Open PowerShell (windows key, search powershell) and run (copy+paste) these commands:

1) cd C:\Program Files (x86)\Steam\steamapps\common\ (or wherever your games are stored)

2)

function du($dir=".") {
gci . | 
  %{$f=$_; gci -r $_.FullName | 
    measure-object -property length -sum |
    select  @{Name="Name"; Expression={$f}}, 
            @{Name="Sum (GB)"; 
            Expression={"{0:N3}" -f ($_.sum / 1GB) }}, Sum } |
  sort Sum -desc |
  format-table -Property Name,"Sum (GB)", Sum -autosize
}

This makes a custom function that emulates Unix's du.

3) du

My output, for example:

Name                            Sum (GB)         Sum
----                            --------         ---
Total War THREE KINGDOMS        33.443   35909039516
PlanetSide 2                    14.001   15033674892
GarrysMod                       12.345   13255649379
Sid Meier's Civilization VI     10.941   11748131253
Cities_Skylines                 10.821   11618987046
Sid Meier's Civilization V      7.706     8274111473
Skyrim                          5.618     6031946296
Counter-Strike Source           4.311     4628808572
SpaceEngine                     4.060     4359200968
ProjectZomboid                  3.272     3513211040
Eve Online                      2.878     3090069433
Risk of Rain 2                  2.023     2172673698
Rollercoaster Tycoon 2          1.252     1344095911
MountBlade Warband              1.233     1324245692
Steamworks Shared               0.885      950038706
Stronghold                      0.834      895090145
Terraria                        0.274      293967879
Rust                            0.173      186144088
Dying Light                     0.127      135939819
Grand Theft Auto V              0.109      116674056
Realm Grinder                   0.044       47739977
Half-Life 2                     0.036       38305374
Counter-Strike Global Offensive 0.035       37479143
Left 4 Dead 2                   0.006        6825097
BorderlandsPreSequel            0.005        5884085
left 4 dead                     0.001        1075611
Unturned                        0.000         188449
Borderlands 2                   0.000         171267
Total War Rome II               0.000          83768
SharecareVR                     0.000           5939
The Walking Dead                0.000            957
The Witcher 3                   0.000              8

The directories at the bottom are nearly empty because I uninstalled the games and there are some residual files, or the bulk of the files are installed on another drive.

This is one of the many reasons that video games are the only reason I use Windows, but alas..