Put the two notes in separately first using Force Durations, then leave note input mode, select both of them and hit T. That should do it.
Hello Daniel, I have the same problem, with tie and enharmonics.
Here is a sample.
I have deleted both notes, O, enter Eb, enter D#. Click outside. Cmd click both noteheads, T. What am I missing? Sorry about this. Thanks!
Eb D# tie.dorico.zip (313 KB)
Daniel, I tried it and indeed it does not work : the second note here is respelled as the first, and by no means I can make this work, I have to use a slur instead of a tie… Is this something that works in your current build ?
The procedure I described above is incorrect, but you can tie between two notes of the same sounding pitch but spelled differently if they are in different voices: select the second note and choose Edit > Voice > New Up-Stem Voice (or down-stem, if that’s more appropriate), and then you can tie them together by selecting both with Ctrl+click, then hitting T.
Thank you, yes this works. Not completely intuitive to make another voice for it 
If I wanted to add a small notehead with an accidental in parenthesis (its enharmonic) beside it how can I do this? I seem to remember a previous post with a link where we could copy it as shift-X.
Dear arco,
I think the little notehead with parenthesized accidental should be available without having to use a text object (only parenthesized notes for pitched instruments still require the shift-X workaround). Have you tried to input it like a grace note ? Or in a new voice, changing its size with the properties panel ?
Thanks Marc, I remember using a copy/paste from the Smufl site a while ago. I can use a grace note, thanks.