Photoshop: Is there a way to stick a Macbethcolor checker automatically under several (thousand) images?

Why do you want to do that, if I may ask?

In any case a Scripts may be a better way to go than an Action.

But your Action could be improved; instead of copy/pasting placing should be easier.
And why the manual part and the second Action instead of doing it in one Action?

»As all the pics are off DIFFERENT sizes, I thought the only way to place the card on the right spot, was to include a stop in the action, nudge it, and continue with a second action«
Actions can be set up to handle differently sized images.
For example you should be able to change the Canvas Size by a number of pixels with »Relative« checked and the anchor set accordingly, then Place the image, Select All and then Align it bottom left.

The thing seems strange to me, though.
If the image is separated and has its profile embedded I would assume it’s up to the printer to maintain a stable output the variance of which should be within the allowed tolerances of the respective printing standard – as they should be able to verify with whatever printing wedge they use.

Not all printers are color managed. Some are still stuck using 19th century methods ("eyeball and hope").

But yes, an action could resize the canvas by a fixed number of pixels (the known size of the macbeth image), but place the macbeth image by percentage in the lower left corner -- without any need to stop and place it manually. With a script you could do even more: by measuring the macbeth image at runtime, or choose among different resolutions of macbeth images, etc.

»If I had known this 3 days ago, I wouldn't had to 1800+ pics (!) with my 2-actions...«
Pity about that; if you have questions about techniques that are not straightforward feature requests you might want to also post over at
http://forums.adobe.com/community/pho...

The size of the image should not matter, if you know the size of the macbeth chart ahead of time.

You just grow the image at the bottom by the height of the macbeth chart (assuming it's already wider), then place the macbeth chart in the lower left corner.

You'd only need to measure the macbeth chart at runtime if you were using multiple sizes, or trying to resize it on the fly for different images.