I had asked how to create midpoints on a line, and I got it to work. I don't have that file anymore and it's been a few years since I've used MFD (184.108.40.206). This worked, but I can't figure out how to do it now. Can someone explain in language that a rusty novice could follow?
Make centroids on line
Copy/Paste all objects in a Drawing linked to the following query into a Duplicate of the [Drawing]
containing the lines where beforehand you deleted all the line objects to have only the table stucture.
SELECT LinePoint([ID],[Length (I)]/2) AS [Geom Center] FROM [Drawing]
Run the query, in the query results table link a drawing with type = geometry column and source = the query table (leave the other fields alone). The linked drawing now contains the midpoints of the lines in
the drawing. This linked drawing table only contains the ID column.
Copy and paste all the points into the (empty) duplicate of the original drawing containing the lines (none of the columns are populated).
Do a spatial overlay between the midpoints and the lines. The drawing linked to the query has to be reprojected to the same coordinate system and precision as the original drawing (and thus the duplicate with the midpoints) before a spatial overlay will work. Since the points didn't have any columns populated (except for the spatial overlay from the HUC drawing), delete all other columns in the duplicate drawing so only the one column was transferred.
I didn't try duplicating the linked drawing and doing a spatial overlay from that. The query did only create midpoints and didn't contain the attributes. You have to Spatial Overlay the original lines to these points and that is why you need the same table structure. You could as well fill in a query of this type
SELECT <list of columns in Drawing>, LinePoint(.... and relink. Now the midpoints have all the original attributes from the beginning.