Creating a map with numbers and a legend explaining the numbers

Create a point layer with two attributes one with the number and one with the text

From the layer styling label, the point with the number attribute

In the styling tab select categorical   

The press the calculation button (the small sigma, a soft Ɛ) then use the concatenate function concat to construct a string consisting of both the number and the Text concat( “id” ,’ : ‘,  “navn”  )

When constructing the expression you find the attributes under  ”Fields and Values. Note the use of double quotation marks around attributes and single quotation marks around the text’ :  ’ .

When you now press classify, all points will be given different colours.

The change them into a single colour select all legend entries and right click and choose change color

Chose the colour you want and press the back arrow and you are done