Ctrl+Z doesn't work properly in Camera RAW filter

What version of acr are you using?

Adobe changed the Undo shortcuts in both photoshop proper and acr starting with CC 2018

(photoshop version 20.0) and acr 11

https://helpx.adobe.com/photoshop/using/whats-new.html#Newmultipleundomode

https://helpx.adobe.com/camera-raw/using/default-keyboard-shortcuts.html

Hi gaelverdauw,

You are correct, you can only step back and then step forward with ACR. You cannot take two (or more) steps back. There is no ability to do continuous stepping back in ACR so there is no way to change key commands to do so.

You might consider using Lightroom Classic which is "ACR with a database." With LR-Classic, you can go all the way back to the first action you took on an image even if you last worked on that image a year or more ago.

Please let us know if this helps you or not.