However, when I select the 4 connectors plus the line and do a Right click -> Align -> distribute horizontally, the green vertical line always gets moved.
Ideally I want the green line to be fixed (locking is only available for components) and the components symmetrically distributed around the line.
FYI: The alignment in the screenshot is only eyeballed at the moment.
I hope my explanation is clear.
Any help is appreciated!
Since Distribute Horizontally leaves the leftmost and rightmost parts in place and then spaces out the rest equally between them, I would manually place the two outer connectors first (drag them by the pad so you can use snapping to line up the pad with the line endpoint), then select just the connectors and distribute.
I find the “Align and distribute” cumbersome to use, although it can be a quick method to put a bunch of parts in a row (or column).
As you’ve already noticed, it acts on all selected objects, The way to use it is to first place the outermost objects manually, then select only the parts you want to “Align and Distribute”.
I much prefer to use the grid myself.
With this you can (temporarily) create a new grid origin and size for component placement.
Pcbnew / Place / Grid Origin (You can snap grid origin to a graphical object or pin).