Hi, I looked into the manual and saw Convert and Modify has a dedicated multi-crop feature or also the possibility to add a "Add/Remove Border (Margins)…" as a batch action.
Nevertheless what I'm looking for seems to (yet) not exist, or I did not find the feature:
1) Load multiple image files of the same dimension into a special window/view.
2) There you have some controls how to show them combined (especially to see the outlying content)
3) Then you can set your crop dimensions accordingly. And then apply on all images loaded in that window.