Missing two entries. The descriptions are for my personal notes. I have no opinion whether they should be included.

3.2 sed commands summary

$           Last line of last input file.
a\          Append text after a line.
text     
a text      Append text after a line.
b label     Branch to label.
   missing  c           Comment, newline delimited.
c\          Change lines with text.
text
c text      Change lines with text.
d           Delete pattern space and start next cycle.
D           If pattern space contains newlines, delete text up to the
            first newline, and restart cycle with the resultant pattern
            space, without reading a new line of input.
e           Executes the command that is found in pattern space in the
            shell, and replaces the pattern space with the output; a
            trailing newline is suppressed.
e command   Executes command in the shell, and sends its output to the
            output stream.
F           Print the file name of the current input file
g           Replace the contents of the pattern space with the contents
            of the hold space.
G           Append a newline to the contents of the pattern space, and
            then append the contents of the hold space to that of the
            pattern space.
h           Replace the contents of the hold space with the contents of
            the pattern space.
H           Append a newline to the contents of the hold space, and then
            append the contents of the pattern space to that of the hold
            space.
i\          Insert text before a line.
text
i text      Insert text before a line.
   missing l [num]     Print the pattern space in an unambiguous form and wrap after
            num columns.
n           If auto-print is not disabled, print the pattern space, then
            replace the pattern space with the next line of input.
N           appends the next line from the input file to the pattern space.
p           If auto-print is not disabled, print the pattern space, then,
            regardless, replace the pattern space with the next line of
            input. If there is no more input then sed exits without
            processing any more commands.
P           Print the pattern space, up to the first <newline>.
q[num]      Print pattern-space and exit with optional exit code, num.
Q[num]      Do not print pattern-space and exit with optional exit code, num.
r filename  Reads file filename.
R filename  Queue a line of filename to be read and inserted into the output
            stream at the end of the current cycle, or when the next input
            line is read.
s///[flags] Match the regular-expression against the content of the pattern
            space and replace with replacement.
t [label]   Branch to label if there has been a successful substitution or
            conditional branch. If no label  the next cycle is started.
T [label]   Branch to label if there has been no successful substitution or
            conditional branch. If no label  the next cycle is started.
v [version] Fail if GNU sed extensions are not supported, or if the requested
            version is not available.
w filename  Write the pattern space to filename.
W filename  Write to the given filename the portion of the pattern space up
            to the first newline.
x           Exchange the contents of the hold and pattern spaces.
y/src/dst/  Change characters in the pattern space which match any characters
            in src with the corresponding character in dst.
z           Delete characters in the pattern space.
#           Comment
{ cmd; cmd ... }  Command grouping
=           Print the current input line number.
: lavel     Label