Update 2025-04-24: Fixed some typos. Content remains unchanged.
Andreas, you mention one important constraint, namely that these placeholders are shown to "users not related to information technology." I.e., these users are not techies, right? 😉
If so, they probably haven't seen this kind of placeholder before, so they will have to guess what it means. Or, worst case, pester you or tech support with questions about what those odd characters are that appear in the UI.
Also, that placeholder allows for literally any string, so the user can't gather any semantic information from this approach. It won't be clear, then, what, exactly, will be shown on the grid line at run time.
In such cases, I prefer to use more verbose placeholders that more clearly reflect what they will eventually be replaced with.
In your example, this could be something like this:
+------------------------
| Delete [data set]?
+------------------------
| Item [product name] created.
+------------------------
| Copied [product entry] to [destination set].
+------------------------
The drawback, as you can see, is that these placeholders take up a lot of room. Then again, this might also help better understand how much room they will need once they display real data beyond the two-character %s placeholder.
