In this previous post (and others) I discussed how to protect spreadsheet cells to prevent your collaborators from messing up your sheets with inappropriate edits.
Google has just made this a little more flexible by allowing you to add a warning text to selected ranges or cells within a sheet that can be edited by collaborators.
To add a warning, select the affected cell(s) and then open the protection sidebar using Data > Protected sheets and ranges…:
Now use the Change permissions button for the range:
Select the radio button for Show a warning when editing this range. In future, collaborators will be able to edit this range, but will receive a warning when doing so:
Hopefully, this will reduce the number of unintended changes made by colleagues who do have permission to edit.