Open Gnome Terminal window and execute 2 commands

gnome-terminal treats everything in quotes as one command, so in order to run many of them consecutively you need to start interpreter (usually a shell), and do stuff inside it, for instance:

gnome-terminal -e 'sh -c "echo test; sleep 10"'

BTW, you may want the window to stay open even after commands finish their job, in such case just start new shell, or replace a current with the new one:

gnome-terminal -e 'sh -c "echo test; sleep 10; exec bash"'

As of January 2020, the -e option in gnome-terminal still works, but throws the warning

# Option “-e” is deprecated and might be removed in a later version of gnome-terminal.

# Use “-- ” to terminate the options and put the command line to execute after it.

You can run the two commands without warning with

gnome-terminal -- /bin/sh -c 'echo test; sleep 10'

And, as mentioned in this answer, if you want the window to stay open afterwards, you can do

gnome-terminal -- /bin/sh -c 'echo test; sleep 10; exec bash'

*answer to a similar question