Which takes precedence - the column nudge value or a custom nudge value?
If there is a custom nudge value (and the condition is met) then that will take precedence over the column nudge value.
Can I use Plus/Minus across multiple cells simultaneously.
Yes, so long as all the highlighted cells are in the same column. The Blotter will automatically apply the correct nudge value for each cell in the selection.
Is there a default Nudge Value for the Blotter like in the .NET edition?
No, this is one of the few changes we have made between the 2 editions. We no longer allow you to a set a default nudge value for the Blotter, as we found that it rarely made sense, and users preferred to 'opt in' and choose to make a column have a nudge value, rather than it having one by default.