When using the “Move and Click” action’s “relative to the current mouse location” setting, the “Get” button is not very helpful — it always returns 0,0! It would be nice if, when using “relative to the current mouse location”, this button worked in two stages: the first would let you position the mouse initially and store that location, and then the second would record the difference between the final mouse position and the initial position. This would let you use “Get” to set up the “relative to the current mouse location” relative distances.
As I'm typing this I realize — classic rubber duck debugging — that one can use the built-in macOS screenshot tool to measure relative distances because it shows the dimensions of the rectangle to be captured. However, this is far less discoverable. (But I'll leave this post here in case someone else stumbles on the same problem and wants a solution.)
I agree, using the drag action with the mouse after pressing SHIFT-CMD-F4 is the best way to measure relative distances.
If you have a high resolution monitor, your life can be made easier by increasing the size of the mouse pointer in System Settings, which increases the size of those tiny numbers...
The bigger you choose that setting to be, the easier it will be to read those numbers. At the largest setting the numbers become roughly as big as your fingernails (ten times bigger than normal.)
As KM can capture pointer positions, do calculations, display results, and even put values on the clipboard ready for you to paste into the "Move and Click" action -- you might like to try and whip up your own macro to get the offset between two locations.
Have a go, and if you get stuck then post whatever you've got and ask about it.
I didn't read this topic thoroughly, but have you tried using KM's Window->Mouse Display? It's quite handy, especially because you can lock the position on a timer, which gives you enough time to click the button and then position the mouse.
