What is the best way to flip multiple frames horizontally at once?

Hello. I am using Animate pro 2.
Now I want to flip horizontally 100 frames animation clip to check errors of my drawings and animation. I think it’s normal to flip a drawing horizontally to find errors in drawing applications like photoshop, so I want to do it in Animate pro.

Now I set the x scale of my drawing layer as -1 to flip all frames horizontally at once, but is it the best way? I wonder if there are better ways. What do you think is the best way to flip multiple frames horizontally?

Just select the first frame in the series and hit the “4” key. That should flip every drawing. Once you’ve checked your drawings, remove the keyframe, F7. You can also do the same thing with a Peg.

Thank you. It works!
I didn’t know Animate has other Flip horizontal command.I used Drawing - Transform - Flip Horizontal, and it didn’t work lol.

One more question, If I want to flip drawings at the center of my scene, do I need to write something on 2 corners of my drawing? I mean, when I flip horizontal in photoshop, I draw something on top left and bottom right corners to flip my drawings precisely, to keep the position. Do I need to do it in Animate?