I currently run the latest version of Euroscope with the latest UK controller pack and plug-in. When using the Edinburgh SMR (EGPH) I cannot add a Callsign to my Departure list as it is greyed out and will not allow me to tick the box to display the column. Other lists do show the Callsign column but again the list option is greyed out not allowing me to deselect it.
All other selections work normally.
That’s probably a question best put toward the VATUK facility engineers as they will be familiar with the specifics of the package and what might be causing it - they may even have seen the error before and know the exact solution to your problem.
Most people in this global forum will only be able to speculate as to the reason and possible solutions.
While I can’t answer your question directly, I would like to highlight a similar report of mine in the old VATSIM forum: List items cannot be deselected for display - EuroScope - VATSIM Community. I’ve never received an answer for this though.
Remember that the list configuration is in a setting text file. If EuroScope doesn’t allow you to change directly, you might at least overcome this limitation by adpating the setting text file accordingly.