Hey there, the camera will follow the player as the dash occurs, which can be tweaked to your liking by editing some of the dash related Platformer+ engine variables in the Project Settings Menu.
Here are the dash settings I used in the project (check Lesson 6s project to see the others, if you like).
Dash Input: Double Tap
Dash Style: Ground
Dash Momentum: None
Dash Through...: Nothing
Dash Distance: 600
Dash Time (frames): 10
Dash Recharge Time: 10
Dash Camera Deadzone: 4
You could look into changing the 'Dash Time' (in frames) setting, in particular. Increasing that will slow down the time it takes for your player character to travel from start of dash to end of dash and reduce the erratic camera movement.
Here are Hauntologys P+ Docs if you need any more info:
https://github.com/becomingplural/GBS_PlatformerPlus/tree/main/docs