Specify audio tempo change at second 4:

asendcmd=c='4.0 atempo tempo 1.5',atempo

Target a specific filter instance:

asendcmd=c='4.0 atempo@my tempo 1.5',atempo@my

Specify a list of drawtext and hue commands in a file.

# show text in the interval 5-10
5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
         [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
# desaturate the image in the interval 15-20
15.0-20.0 [enter] hue s 0,
          [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
          [leave] hue s 1,
          [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
# apply an exponential saturation fade-out effect, starting from time 25
25 [enter] hue s exp(25-t)

A filtergraph allowing to read and process the above command list stored in a file 'test.cmd', can be specified with:

sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue