I read the: "Subscript labels in QGIS legends" thread.
I would like to follow up on this for nautical notations.
One Z-value, when displayed, must be displayed in normal script and subscript.
For example: If you want to display the value 9,3 it is supposed to be displayed in the nautical notation as: normal script: 9 subscript: 3
Is there a way to format the label of the value in this manner? Note that heights above datum have an underscore under the whole digits.
![how i display it now[![][1]](https://i.sstatic.net/1kBHj.jpg)
]2
Progressing from Albert's comment if you separate the whole and decimal numbers as separate attributes you can duplicate the layer and have both parts as font markers which will allow you to colour via depth
Select the 'Assistant' from the fill color options
Select required colour ramp
One idea would be creating a point layer of your labels. The regular underlined value would be a label and the subscript could be a font marker. You can create an expression in Character(s) to input the desired value.
Moving your anchor points of the font marker:
and the quadrant placement of your label:
can create the effect of a subscript. The following image has been made using this method.
I solved it like this.
It's not elegant, but it works.
The label displays a value called "VALSOU"
text for label "whole":
if(to_int( "VALSOU") > "VALSOU",(to_int( "VALSOU") -'1'),to_int("VALSOU"))
This killed of the decimal from the whole number. I added the -1 because the [to_int(] rounds of the number. Without it 5.6 becomes 6 and then I'm off by a meter in my chart.
text for label "decimal":
CASE
WHEN to_int("VALSOU")>"VALSOU" THEN to_int(("VALSOU"-(to_int("VALSOU")-'1'))'10')
WHEN to_int("VALSOU")< "VALSOU" THEN to_int(("VALSOU" - (to_int("VALSOU")))'10')
END
This killed of the whole number and displays the decimal as a whole number.
After this it's a matter of changing the position of the label "whole" and "decimal" relative to the geometry and eachother. 
Have a look at the Python custom expression functions in this answer: Achieving Super or Subscript graticule labels in QGIS Composer windows?
They will allow this labelling style to be achieved without involving multiple components to the label and fiddling with offsets.
I used a similar method to CaptainAhab
Whole number label (left of depth):
floor(abs($z)) Decimal (right of depth)
IF (ROUND(ABS($z)-'0.05'-FLOOR(ABS($z)-'0.05'),'1')*'10'='10','0',ROUND(ABS($z)-'0.05'-FLOOR(ABS($z)-'0.05'),'1')*'10') The 0.05 value in the expression above ensures that a depth of 5.37m is labelled 5.3 deep instead of 5.4
