Hi @susannah-slv, welcome to the forum! Thanks for sharing this. I’ve been able to replicate this in 3.9.5, though I think this issue will be fixed in the upcoming 3.10 release. There have been a few improvements to the “apply operations” command which should make this issue harder (if not impossible) to come across.
Specifically, before a user can apply the list of JSON operations, they must first select which columns in the project map to the columns referenced in the operations. In this example, it’s clear that there is no valid column to map to “Column”. I’ve attached a screenshot of that second screen below to help clarify what I mean:
As for the release timing of 3.10, I’m hoping we can have a beta release some time next week. The OpenRefine 3.10 release timeline thread will have more details as the release comes together.