After creating a watcher and a variable under it in MCS, I cannot assign the variable to the watcher.
The watcher appears grayed out and is not editable.
This issue was discovered using UIM 8.51 and MCS 8.50, but the information in this article is generally applicable to all versions of UIM / MCS.
After creating the profiles/watchers/variables, restart the MCS probe (deactivate/activate). This should allow those fields to become editable once again.