When the message in a grid cells gets too long you get stuck. No way at all to hit the X at all. No way to click and change the value either.
What can I do about this?
I think you may have raised this before in another post: Grid meets read only and constraint
We do have this as an internal issue in our backlog, however it is not in the current 3.10 release or near future development plans as high priority, currently you are the only user to report this issue.
Can I suggest you submit this issue as a bug via Esri Support. Our Support team will assign an official bug number for your records. This number can be used to search for and subscribe to the bug on the Esri Support site. If the issue is reported by other customers it will be attached to the same bug report, which helps us assess the impact of the issue and prioritize it accordingly.