See parent task.
To sum up, this means
- Invert the behaviour of the Alt key to make the Properties affect multiple objects. (No modifier = affect all selected. Hold Alt = Only active)
- We already have a visual affordance when holding Alt to manipulate properties for multiple objects:
We should just show this while hovering (or even always) for all properties where this is supported.
That is actually all that's needed.
- Implement relative value editing, using a symbol. Maybe =? Changing values to be three less could by typed as "=-3"