I’m trying to do something similar but am not sure if supported:
Is there a way to reference “self” in the anchor?
I’m hoping I can do something like:
pos base @myGroup <anchor ${self:anchors.bottom.x} ${SomeNumberValue}> mark @mark_bottom' @lettersFollowing;
EDIT: To clarify, I want to use the x already defined in bottom but in certain context set a fixed new y value. Ideally I could do this with a large group instead of needing an individual entry for each letter. I know I can also do this via context anchor within the glyphs as well but if the above is possible that would be much easier to manage.