How do I get 4. + 4. meter in LH?
I imported a Music XML file and is not sure if that corrupts things. Should I reset (how) any XML import before further work in Dorico?
To get an independent (local) time signature in one staff, type the time signature into the Meter popover and then hold down the ALT (OPT) key while pressing Return/Enter.
Note that the measure lines will not align if one does this. To do that one needs to fake the different time signatures and use hidden tuplets.
Using separate time sigs on a grand-staff style instruments will cancel the bar lines that join the two staves for the entire system containing the distinct time signatures.
If you just want dotted quarters in 3/4, you can use Force Duration. The trick to apply that on existing notes is to first change the note value to eighths (type ‘5’), then type ‘o’ to switch force duration on, and then restore to dotted quarters with ‘6.’ You can even do that with many notes selected.
If you want the left hand to even have a 6/8 time signature, then you can add it locally (just for 1 staff) by putting the caret in the LH staff, typing shift-T, 6/8, and then pressing the Alt key while pressing Enter.
(Ninja’d by Derrek)
Thank you. I adjusted it so it is 4. + 4. in LH. Some manual work, but a short piece, so no problem. I thought there would be a command for this. I once used a notation program where you would type “ba 4.” and it was all sorted out. Perhaps for a future feature?
This specific case has been discussed many times here. Search the forum for “force duration” and you’ll find lots of threads.
The upshot for Dorico is: The tied notation is generally correct in 3/4 meter, and using force duration as you did to get the second dotted quarter is the proper method.
If I had 100+ bars of this rhythm, I might use the hidden-6/8 suggestion. But usually it’s easier to copy a bar with the desired duration forced and repitch it.
Or just put the piece into 6/8, if that is the split Mats wants.
One could also try to put an interchangeable time signature to good use. I remember doing this, but at the start of the tune it will show both 6/8 and 3/4.
Might be a way to have everything aligned though…
B.
I tried the alternative, to hide 6/8 meter in LH’s second bar. It worked well, but can you do the same from bar 1, i.e. have a 3/4 printed but a hidden 6/8?
Ah, but one bar of force duration couldn’t possibly hurt anyone? 
B.
Certainly not a big problem. It is easy to do, but there is beauty in simplicity. I’m used with another system where I wrote “M1 (M2)” and meter M1 got printed and M2 was what ‘counted’ and set the rules, no matter what M1 and M2 was in relation to each other. I’m learning the Dorico way now. It is interesting and quite fun.