Great to hear that you got it operating snappier!
One last tip to speed up the finding of images – if your layout and screen arrangement is somewhat consistent – is to shrink the area the image is searched for. Especially for high-resolution monitors, this can offer quite a substantial speed-up.
Defining the area is most easily done by pressing the 'Get' button and drawing a rectangle around your area of interest. If your secondary display is arranged to the left of your main display, you might get negative values; if to the right, a value of more than your main display width resolution; etc.
If your layout is not that consistent, even drawing a very generous rectangle over half or quarter of your screen will help.
The pixel values of the area parameters are by default absolute values, relative to your main display's top-left corner. But the values can be made relative to, for example, the focused window, by using the WINDOW()-function. This way, you could move the window around, and even change display arrangement, so long as the layout within Cubase does not change relative to your selected window edge/corner.
As an example, relative to the top right corner of the focused window, could look something like this:
This will define a rectangle of 300x150, hugging the right edge, 500 pixels down from the window top edge.
While setting up more convoluted areas like this, a "pro-tip" can be to use the Highlight Location action as a tool to check where your defined area is pointing to. Set it to rectangle mode, and the same x, y, width, and height (→, ↓, ↔, ↕) values as your area. Placed in a loop, you can even see how it follows the focused window while moving it around!
(P.S.: Defining a tight area relative to the window frame like this can take you dangerously close to simply defining the exact coordinate you want to click — something that could take finding of the image out of the equation entirely!)