There is no feedback when you are editing the condition for a conditional format to appear. For example equal to 'A' doesn't work (it should be equal to "A")
Steps to reproduce:
1. Create document
2. Type "A" in first cell (without the quotes)
3. Format -> Conditional Format -> Condition ...
4. Choose [Cell value] [is equal to] [A]
5. Apply style [Header style]
No warning whatsoever that this is not going to work, similarly, 'A' is also not leading to any warnings
When you type in a cell =FIND('A';A1) in B2 (instead of the correct =FIND("B";A1) ) the preview should at least show "#VALUE!" like when a formula contains an incorrect value (I believe that even this warning should be improved (but that would be a different issue))
reproducible with LO 22.214.171.124 (Win 8.1), I would agree that a warning dialog would be better
Marked as RESOLVED-WORKSFORME
The dialog now reports "Strings without quotes are interpreted as column/row labels"
126.96.36.199 on macOS 10.12.4