It's a Prusa MK3s but the issue I believe is in the slicer
I created my object in Fusion360. It is some interlocking parts so it has a finger and a slot. I enabled supports for both sides.
On the side with the slot, it creates supports as expected, but it does not lay the first bridging layer in an ideal direction, and earlier prototype which didn't go very well, but on this part it laid the bridging layer longways, which amounts to a bridge the entire width of the print bed, which definitely didn't go very well.
I tried to find a way to specify which way the bridge should be laid, but it seems that especially with supports, the slicer itself should be attempting to "anchor" one side in the support.
I'm very happy to work on this issue if someone can offer some pointers on where to start looking in the source!
This is the 3mf file https://gist.github.com/richo/a23fd2e4d4e4bfcddcf7f491e37bacb6
Oh, one quick update. I found the Bridging Angle parameter in print settings, but it's global so it appears that with bridges at right angles there is no setting you can use that isn't a compromise. My intuition is that the slicer should be optimising for either the shortest path on the bridge, or maybe shortest path with a small angle to let it "build" out from a corner. but, as I said I am very new to this so I'm not trying to be very prescriptive.