1. Open a new worksheet
2. Place some cell with values
3. Apply conditional Formating to cells, for example: 1 - Red, 2 Blue, ...
4. Try to select the same range of cells and go to Conditional formating.
Now you can see all conditional Format you have defined, but you can not alter them you must create a new one if you need to change any cell format.
The Conditional format screen should permit to alter the conditional format applied to the cells.
I am pretty sure that this one is a DUP of "Bug 51555 - FORMATTING Not possible to add Conditional formatting ", although nearby all relevant information is missing.
A report without information concerning LibO Version is not very useful. Can you please read <http://wiki.documentfoundation.org/BugReport> ?
Please feel free to reopen this Bug if you find evidence that we have an independent issue here.
*** This bug has been marked as a duplicate of bug 51555 ***