What is the best/easiest way to control print speed?

What is the best/easiest way to control print speed? I want to slow down the printer speeds for testing.

In Octoprint - speed rate.

Do you mean “Feed Rate”?

Yes. Sorry for mistake.

I tried that and it didn’t seem to effect the speed.

Just tried it again and it worked! Go figure. Thanks

Yes. Click button with percentage value.