Use the Jog speed slider to the right - as the jog rate has always depended on Grbl's Max Rate, the input field was well confusing, the slider makes more sense. Tune your Max jog rate in Max Rate under Grbl Settings, and then the slider is some percentage of maximum. The text field worked the same under the hood, it rarely moved at the feed you typed because Max Rate and Acceleration governed it for you
I often do some straight cuts at 20”/ min Always different length, so not worth creating a file. Never noticed an issue with speed not being exact. Is there a shortcut key to get feed rate to exact percentage? Overall, extremely impressed with controller software. Might just roll-back to previous version.
Also see the Slot cutting macro: Getting started with Javascript Macros in CONTROL / Library of Macros created by the community