Welcome to the forums @oebeltranm
The only ‘workaround’ that I know of, and it only works reasonably well with straight lines, is to draw the line from the start to the end, then back to the start again, and then to the middle, adding the arrowhead at the end of the line (which is now in the middle of the line).
(Or you can draw the line from the start to the end and then to the middle but you will need to ‘flip’ the line to get the arrowhead pointing the ‘right way’.)
The length of the line can be changed using the Move Tool or, more awkwardly, with the Node Tool.
It’s not ideal but it might be useful for some non-complex requirements where accuracy isn't important (the arrowhead will not be exactly centred).
You might be able to do something with Constraints in Designer but I think that will only be even more awkward, requiring more layers.
Maybe someone else has a better solution and will post it here.
