Each marker icon can be disabled within the settings.
Check the appropriate submenu of "Marker icons" -> e.g. "Gear" -> "Enable/Disable" and enable the marker icons in there.

Disabled icons
-are not shown ingame in the context menus anymore
-cannot be used for marking items
-are not shown in the inventories anymore
-inside the setitngs the depending settings are not changeable (greyed out)
-dropdown boxes for marker icons are showing the entries "red"

You are able to keep the protection of disabled marker icons so items not showing the marker icons currently, because it's disabled, will still be protected!
There is a setting to enable/disable this behaviour:
AddOn settings -> FCOItemSaver -> Icons -> Deactivated icons

To remove the marker icon from them you need to enable the marker icon though in the settings again!

-> Same applies to normal marker icons and/or dynamic icons.