The manual is for general description of the tools, I think writing step-by-step tutorial won’t be in the scope. However, if you think it needs improvement we are open to suggestions. When you learn Krita enough you can point out the shortcomings and let us know where to improve.
As for your problem here is a solution: There are two ways to create a line with dots, choose anyone according to your needs.
Vector layer way
Step 1 :
Open Krita and a new document. By going to File > New (I hope you choose appropriate size and other settings for this)
Step 2:
Click on the arrow next to the plus icon in the layer docker, Choose vector Layer. A new vector layer will be added.
Step 3:
Choose the Shape selection tool from the toolbox. It is the arrow icon. Select the line you drew on the canvas with this tool.
Step 4:
Go to tool option docker and in the stroke section (the middle tab) change the thickness. And change the line style to get a dotted line.
Here is a GIF to help you visually.

Brush tool way
Step 1 :
Open Krita and a new document. By going to File > New
Step 2:
Click on the brush tool in the tool box to select the raster brush tool.
Step 3:
Choose an appropriate brush preset from the brush preset docker. Then press F5 or click on the Edit Brush settings icon (the icon will show the brush you have selected) in the top toolbar. This will open the brush editor.
Step 4:
Go to the brush tip sections and expand the scratch pad just in case if you need to test the brush.
Step 5:
In the brush tip section, disable Spacing Auto checkbox and increase the spacing of the dab. This will give you a brush with dots at regular interval. Test your brush in the scratch pad.
Step 6 :
Choose the line tool from the tool box and draw a raster line on a paint layer. It will have dots now.
Here is a GIF to show this way:

Note :
Line tool works on both vector and raster layer. Line drawn on the vector layer can be edited later but line drawn on raster layer will be editable in limited capacity as it will be raster.
As you can see this is a tutorial very specific to a certain task, this can not be in the manual. The manual can be a place to show what individual tool or feature does but not a place to add tutorials. As an exception we have added some common tutorials if there is demand we can add more of it. But help is really appreciated in improving the manual.