After a long talk with Dave, I thought (operative word: thought) I had it sussed.
Today I am trying to restructure some things.
Slowly slowly. I get it.
But this is just getting beyond a joke.
Looking at the screen shot this is where I am stuck.

Yes, I am probably still doing it wrong. Not having DIRECT contact is killing me.
(No offense to Dave)
It is more this covid crap.....
Anyway: I have 2 pedals. Badly built - yes. But for show.
I have one sliding back/forward ok. And a 10 degree title on the pedal. Just to show off.
But then when I get to the second one... It all falls over.
If I don't connect the pedal, it seems to fail, so I can't get that.
The post and pedal don't line up - or maybe they do as I have fixed it. BRAIN FAILURE!
The RIGHT (looking from where you would be if you are using them) is giving the grief.
I create the joint and it slides. (I learnt that I had to stop the rotation to make things nicer)
All +/- 80mm.
But as soon as I either put the pedal on, or *link* the two pedals.... I am luck to move it 20mm.
I've been at it for HOURS - literally. (Honestly even)
Dave was explaining the hierarchy of joints. I thought I got it.
But Fusion has other ideas.
I've tried all ways of ordering things. I step back one step and it works.
Apply that last step and... all falls over.
Please (someone) have a look at/in the time line where shown and explain why the joints are messing up.
(On a tangent: Usually when I export files they are .f3d or .3mf Today they are .f3z and neither of the others are visible. What's going on?)