QGIS 3.6 - Modifying data defined override-expression?

Question

Is there a way to alter the data defined override expression? I have a points layer which I label with one of its attributes. The attribute table also comes with a field for an offset from point-value for correct displaying, but the format of this field doesn't work with the override on these two points:

1. Datatype in the table is int, Override is looking for string
2. Table values range from 1-9, Override is looking for 0-8 (and starts from top left quadrant, instead of bottom left)

I would like to avoid making a copy of the layer and alter the values, as this is a layer that I sync from an external source.

Here is the current expression:

Data defined override
Active: no   (ctrl|right-click toggles)
Expected input:
int
[0=Above Left|1=Above|2=Above Right|
3=Left|4=Over|5=Right|
6=Below Left|7=Below|8=Below Right]
Valid input types:
string
Current definition ():
undefined

And this is what I would like it to be:

Data defined override
Active: no   (ctrl|right-click toggles)
Expected input:
int
[7=Above Left|8=Above|9=Above Right|
4=Left|5=Over|6=Right|
1=Below Left|2=Below|3=Below Right]**
Valid input types:
int
Current definition ():
undefined

Best regards /Jeston

Answer 1

Great thing about data defined override is that you may not only use a column, but also any valid expression producing valid values for the thing you like to override (this is either or, if you add an expression, you needn't add a column, and vice versa). Simply click the override button, go to edit and enter the following:

CASE
WHEN "override column" = 1 THEN 6
WHEN "override column" = 2 THEN 7
WHEN "override column" = 3 THEN 8
WHEN "override column" = 4 THEN 3
WHEN "override column" = 5 THEN 4
WHEN "override column" = 6 THEN 5
WHEN "override column" = 7 THEN 0
WHEN "override column" = 8 THEN 1
WHEN "override column" = 9 THEN 2
END

"override column" is your column name and needs to be replaced, and I assume your column has integer values. If this is not the case, you need to place single paranthesis (') around the first number in each row.