If you teleport or shift (as the conjurer's ability)
Do you take the broom with you, or is it left behind?
In the past, I've had it that you leave it behind unless you're carrying it, or in the case of ioun stones, it's 'bound' to you.
If you're riding the broom, does it just come with you compared to say a horse which would be left behind (unless it was a designated creature via teleport) ?
This brings up another question of say 'dismounting' someone from a broom. Does it follow disarm rules? As the caster may have a staff held in two hands so they're holding it with their 'legs'. Or is a bull-rush or re-position required?
By this logic, can someone 'mount' a large bar of gold, and simply use dimensional steps to move it some distance by virtue of it being an 'attended object' ?