Not sure what you're looking for, but this is what I get. It looks okay to me.

Set your time signature as 4, dotted eighths, to display as 12, eighth notes.

APOLOGIES; That’s 4, dotted QUARTERS!

... read 4 dotted quarter notes.

It can even be done afterwards with Utilities -> Rebeam. And the manual way is the slash key applied to the note on the right.

Thanks to all of you.  The rebeaming worked once I could get the composite to recognize the groupings, which I had to put in as 1536 EDU's to make the rhythm show up as dotted quarters.  Clearly it is simpler to tell a piece how to beam before writing any music; but I had written a piece in 9 8 and then realized I had used the wrong time signature (old brain) so converted to 12 8 which segues into 4 4 (so it is not a traditional slide).  If there is an easier way - like choosing the right time signature before starting - I usually don't find it. 

… The rebeaming worked once I could get the composite to recognize the groupings, which I had to put in as 1536 EDU's to make the rhythm show up as dotted quarters …

That is the hardest way to do it.

Michel Herr showed the simplest solution - which does not require going into the dialog Composite Time Signature:

Thanks to all you community experts for this! Was having trouble with this exact issue! Trying to transcribe the 2nd mvt. of the Brandenburg No 3 to string quartet, and just 2 16th notes would beam together in speedy entry. Thankfully, I searched and found this solution posted 6 years ago - and it worked!