I need to place two test point pads such that the center to center distance should be 4.9mm
One simple way is to first snap the grid origin to the center of one of the pads, and the grid resolution to 4.9mm.
Another method is to select one footprint, right click and then from the context menu select: Position tools / Position Relative to and then use the other footprint as the reference. Make sure that you select the same feature (for example a pad center) in both footprints. then you can simply type in numbers for the relative position in the X and Y coordinates. This function works quite well, but it’s not very intuitive, so you may need to experiment a bit before you understand how it works.
A third method, is to first open the properties of one footprint, and then copy a coordinate from the X and/or Y position:
And then you can paste that coordinate in the properties of the other footprint and simply add “+4.9” after it. You can also add units such as mm or mill and KiCad both converts those numbers and adds them.
4.9 is ‘round’ distance so I see no problem.
I am all the time working with grid set to 0.1mm. So just seeing cursor position (bottom of screen) when placing one and second would be enough (adding 5 and subracting 0.1 in memory is still possible for me).
And one more: if the grid is 0.1, go to the center of the first footprint. Press spacebar. Select the second one and start moving it from its center. You can see the delta coordinates relative to the first one in the bottom of the view, and with a little bit of zooming you can move to the wanted relative position without calculating.