The radio's special memories - marine channels and BC radio channels - can be added to memory banks using the Special Memories tab.
Remember that entries on this tab are included in the count for no more than 100 memories per bank.
Setting and un-setting the cells with X's is done by selecting the cells to be changed and then using the command "Fill with Bank selected X's" or "Empty of Bank selected X's". Multiple rows and columns can be selected at the same time, and Empty memories within the selection are automatically ignored. The Delete key can also be used to remove entries.
It you only have one cell to change you can also use the keyboard. Any character(s) typed will be converted to a single X.
These commands are available on the Banks menu and the right-click pop-up.
An alternative is to use the keyboard shortcuts CTRL + B for Bank fill, and CTRL + E for empty.