In this example:
I feel like it will be easier to read and more standard if instead of two.
For some reason, if I use a quarter note instead of two eights, dorico does use a half-note:
It’s unclear to me why those situations differ in terms of tying rules.
Anyway, is there a way to configure Dorico to use a half note in the first example as well? Where is that configuration?
No, for the time being Dorico won’t show a half note by default in that specific combination of rhythms. Dorico will always break notes that cross the half bar, except in particular combinations of short-long-short syncopation patterns; however, if either of the “shorts” in the short-long-short pattern are not a single note, then these rules for syncopations won’t apply. This is something that we plan to add further options for in future versions.
For the time being, you will need to use Force Duration in this kind of situation.
Thanks for the detailed reply. Can you post a link to explain how to use force duration?
I do believe that in this particular case “e e h q” would be more common than “e e q_q q” in existing score repertoir. I don’t think I’ve never seen two quarter notes tied in the same measure.
The short trick is: select the tied note, and type 6 o 7 (that’s a letter o). Make sure you’re not in insert mode, to avoid shifting around the rest of the music.
Emm, I have a more unique situation:
I want to see “_e e_h q”
I couldn’t figure out how to accomplish this with force duration
Select the tie and cut it (u). Select the first crotchet and force duration (o7). Select the quaver, force duration and make the tie (ot)
I tried, that, it swapped back to how it was originally on the last step…
You forgot to force the duration of the quaver before you made the tie.
Sorry my bad, I though “quaver” is a “quarter” 
Anyway, I tried it again and it worked. It is weird that I need to force the eight, even though the eight doesn’t change.
This weirdness, as you call it, is fundamental to Dorico, which treats tied notes as a single note and notates it according to your notation settings. You override those settings by using Force Duration.
The reason for this is when you tie two notes together, they cease being two separate notes, and become one single note all together. The properties and settings of the first note in the tie chain then applies to all subsequent notes it “eats” later on in the tie.
Therefore if the first note doesn’t have its duration forced, subsequent notes take on that state as they get tied.
This is why, in situations where you want specific durations represented within a tie chain, we recommend forcing the duration of all notes, then tie-ing left-to-right along the tie. It’ll produce the cleanest results.