The way I know to flip a single articulation is as follows:
The way I know to flip many slurs is as follows:
However, is there a simple way to place many articulations and slurs correctly when there are two voices on a staff easily without doing what I mentioned above per position?
Is there no global option for this kind of work?
In the following example, I cannot even select the articulations for down-stem voice 1 because they appear on the notehead of up-stem voice 1.
I hope that this could be fixed as soon as possible…
The bigger question is how you got the original results, and why.
By default in multiple voice situations Dorico will always put articulations stem side. If they’re a mix of articulations of force and articulations of duration then while selecting individual notes will reveal the relevant Placement property, selecting a bunch of notes won’t reveal that property - as there are different set of properties for Articulations of duration and Articulations of force.
Selecting the whole passage and going Edit > Reset Position will reset these properties in bulk. Filter just notes, first, if there are other things whose position you don’t want to reset.
Or if you really do want to put the articulations notehead side, you can do that by selecting the relevant notes and setting the relevant Placement property, which will be in Articulations section of the properties panel (in Write mode as well as Engrave mode). If it’s a scenario like your first screenshot, with overlapping pitches, note that you can select just the upstem note by clicking on its stem. If you only want to select the downstem note, select its stem.
Thank you for your kind answer!
I got the mix of the two voices from a special copy:
The two voices are originally almost the same melody (slightly similar to heterophony) from a tune. I first dictated two voices on two different staves, then copied the melody onto the second staff, and pasted the “Down-stem voice 1” onto the first staff.
Then I added the articulations, but they are automatically placed on the note side, and I manually moved them to the stem side.
Oh, it is really strange why my Dorico places them note-side…
That solves my problem. Thank you very much!!! 
