The service manual says the distance between the fixed arm and the tonearm bars should be 7.7mm. That matches up with the Beogram 4004 transport fitting for the arms. I find it helpful to attach the transport fitting while I make my initial adjustments of the tonearm positioning bar.
The tonearm needs to be parallel with the fixed arm at the prescribed 7.7mm distance and the tonearm raise/lowering lever needs to meet the positioning bar right in the center of the triangular slot (circled in red above).
These adjustments take quite a few iterations even with the nice head-start provided by the transport fitting. One reason is I am also adjusting the initial position of the counter weight and that adjustment affects the tonearm positioning bar.
The goal is to have the arms parallel and the tonearm balanced so when the lowering lever lifts up from the triangular slot so the tonearm is free to lower, it lowers straight down without any sideways movement. When the tonearm lever lowers into the triangular slot to raise the tonearm, the arm must raise straight up without any left or right movement.
I was able to eventually get this arm assembly adjusted where I wanted it. The final adjustments of the lowering limit and tracking weight fine tuning will be done later when the Beogram is re-assembled.
I checked over the arm position from the front and I think this assembly is ready to move on to the next stage.