Sometimes in the score there are five measures in one line and three measures in the next. I would like to change it . but I can not find the shortcut
And also I wonder how to combine the two eighth notes like this in 6/8 and change the direction of stem on the second eighth note.(I try the shortcut but nothing happened,if I change 6/8 to 3/4 then it’s ok.)
Welcome to the forum @Zhuoyang_Han - for setting a fixed number of bars per system, see here.
For your note grouping question, that is correct for 6/8, which is a compound time signature - each bar contains two beats, each containing 3 eighth notes. Changing the time signature to 3/4 shows 3 quarter notes because 3/4 contains three quarter note beats. If you have Dorico Pro, you can also access different defaults in Notation Options.
You can flip the stems of each note in tie chains in Engrave mode. However, if you’re flipping them because you’re recreating music that also has notes in an up-stem voice higher on the staff, you should find that Dorico will update the stem directions automatically if you input the notes in the other voice.
Thank you so much for your help 