This is a MASSIVE problem I’m having since I ever remember starting using libreoffice a few months ago. Recently I installed the experimental version but the issue persists here too.
Any time I create a new style, no matter which way (from scratch, from selection, from the conditional formatting contextual menu…), after saving and exiting the file, it will be lost forever. Entering the file from any PC, including the same one it was created with, the created style will be missing, and any cell assigned to that style will be changed to a completely random one among the default ones. Cells that didn’t get applied a style but rather visually modified with the other tools (background fill, text color, etc) will keep the graphical formatting.
This bug renders impossible using conditional formatting and saving styles to be used later or in other files. And conditional formatting is more than essential in accounting entries, mill rates, payments tracking, etc, for how packed with values, numbers and text are.