Create own grouping in Qlik - qlikview

Question

I have a dimension
Group:
A
B
C
D
And Data:
+----+--------+-------+
| ID | Amount | Group |
+----+--------+-------+
| 1 | 10 | A |
| 1 | 20 | C |
| 2 | 30 | A |
| 3 | 40 | A |
| 3 | 50 | B |
+----+--------+-------+
In my data, it will not have group D exists, the logic will be if exists in group A, but didn't exists in group B or C, then it will classify to group D
in above example, it should have a "hidden" data as
+----+--------+-------+
| ID | Amount | Group |
+----+--------+-------+
| 2 | 10 | D |
+----+--------+-------+
I know that I can create that in Load script, but my data are stored as month by month, which means it can create triple or more dummy data.
Question
So is it possible to use the expression to create grouping?
In my bar chart, I have a dimension:
=IF(Group = 'A', null(), Group)
For measure, my idea it may be
Group D:
sum({$<Group = 'A'>} Amount) - sum({$<Group = - 'A', ID = P({$<Group = 'A'>} ID)>} Amount)
Other Group:
sum({$<Group = - 'A', $<ID = P({$<Group = 'A'>} ID)>} Amount)
result table:
+-------+--------+
| Group | Amount |
+-------+--------+
| B | 50 |
| C | 20 |
| D | 30 |
+-------+--------+
underlying table:
+----+--------+-------+
| ID | Amount | Group |
+----+--------+-------+
| 1 | 20 | C |
| 2 | 30 | D |
| 3 | 50 | B |
+----+--------+-------+

Answer 1

Here is my solution to your problem,
Your examples are a bit incorrect, as the ID 2 has an amount of 30 instead of 10 in your example:
What I would do is something in these lines.
IN Script:
DATA:
LOAD * INLINE [
ID, Amount, Group
1, 10, A
1, 20, C
2, 30, A
3, 40, A
3, 50, B
];
Left Join
LOAD ID, Concat(Group,',') as GroupLink Resident DATA Group By ID;
Then in your dimensions:
=If(WildMatch(GroupLink,'A') AND NOT (WildMatch(GroupLink,'B') OR WildMatch(GroupLink,'C')),
'D', Group)
Then in your expression:
=Sum(Amount)
Will yield the following:

Answer 2

I think you need to add a calculated dimension in your chart with aggr function