I don't feel sure about your actual needs. The question as I understand it mixes up changes in formats, contents - and probably even formula results and or cell dimensions.
The mentioned cases need different treatment, and only for the editing of contents there is a simple solution: Every sheet raises a respective event if the content of at least one cell was edited. You can assign your routine (script) to the dialog's list item 'Content changed' accessible via the sheet-tab's context menu item 'Sheet Events...'.
Please note:
-1- Despite its name the event is also risen if the content was edited, but in the end set unchanged. Even using 'Del' on a blank cell raises the event. The event is not risen if an entered process of editing was cancelled ('Esc').
-2- The called routine gets passed one parameter (say pEvent) telling you what cells were edited.
-3- The value of pEvent is an object that can be of two different types: SheetCellRange or SheetCellRanges. The case of a single cell is subsumed under the first case. The cases must be distinguished by your code.
To listen to any different kind of changing cell properties - if supported at all - will need to explicitly register a listener. I doubt if you will get a respective tutorial in a forum. You will need to study "the literatur", I'm afraid. Be prepared to experience problems on your pursuit of information.
Example: https://api.libreoffice.org/docs/idl/...
===Edit1 2019-03-24 18:31 UTC===
With respect to my comment to the answer by the OQ I post the following code.
Sub markiereBearbeitet(oEvent)
REM Wolfgang Jäger 2019-03-25
oDoc = ThisComponent
oSheet = oEvent.Spreadsheet
If Not oEvent.supportsService("com.sun.star.sheet.SheetCell") Then Exit Sub
If NOT (oEvent.CellStyle="csForEditing") Then Exit Sub
oEvent.CellStyle ="csEdited"
With oEvent.CellAddress
oNeighbour = oSheet.getCellByPosition(.Column + 1, .Row)
End With
oNeighbour.String = "bearbeitet"
End Sub
To get it work as intended you need to create the cell styles "csForEditing" (which may otherwise be identiacal to "Default") and "csEdited" ("bearbeitet"), and to apply "csForEditing" to all the cells you want to apply the Sub when edited later. This way you may edit other cells without triggering the "bearbeitet" effacts.
Having finished you can filter the rows containing the keyword in the cell right next to the edited cells.
Please note that a script cannot ask a cell for the format (attributes) applied to it for the view by ConditionalFormatting.
As generally formulas are not aware of any history(¹) (previous states) they also are if used in CF.
Also if you use the 'Content changed' event (see below), you only have access to the ContentAfter and never to the previous content - except you explicitly saved it elsewhere precautionary.
(¹) The only rather fragile restriction is the access to the previous-current value for a reference during recalculation under iteration.