I often do this for upside-down Ronin shots
Here’s my work around:
-Bring the clip into the timeline
-Go to effects: “transform”, and apply that effect to the clip
-In the transform effect setting, change the rotation to 180 degrees.
-Copy the effect, then delete it
-Go to the “master” tab on the upper left of the effects controls
-Paste the Transform effect into there.
Now the whole clip will have this effect burnt into it, even if pulled from project bin again. It will also pull up in the source monitor with the image flipped. To get the effect applied on all the clips, they will need to be pulled into the timeline and have the transform effect pasted into the Master tab of each clip individually. I don’t know of a faster way to apply it to a batch of them at once – because unless you specifically click on the master tab and paste, then it will only paste in the regular effects tab.
Hope this helps