Repro: 1. Create spreadsheet. 2. Add some data. 3. Select some cells and add conditional formatting, e.g. using Format > Conditional Formatting > Condition. 4. Now click Undo. Expected: Conditional formatting is removed. Result: Conditional formatting is preserved, as can be inspected in Format > Conditional Formatting > Manage. Instead, the UNDO action undoes the previous edit operation. Note: if one created a new style in step 3, this style will be removed by UNDO. The conditional formatting (while still preserved) will not have any style associated and thus might appear removed.
Markus Mohrhard committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=f2431c944376433219eb7eb704e9b21589f201f5 add undo action for conditional formatting, cp#1000050, fdo#77381 The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.