I have exactly the same question, because MacFamilyTree, which I use, seems to have no facility to identify DNA match persons. I have therefore done two things. Firstly I attach as media the symbol for DNA to the match person, so instead of a photograph I see the symbol. I can put the cM into the person's name but only as a suffix but it doesn't appear in the tree until I search for it.
The second thing I've resorted to doing is to create a Word diagram using text boxes with names inserted and lines from the shapes library to join them up. I also fill the relevant text boxes with colour to indicate how the DNA I'm interested in descends to my living matches in each case.
I am astonished that the FH software world seems to have ignored how DNA is now occupying the lives of so many of us as we seek to discover our ancestors.