Dear libreoffice,
When I make changes to a list style in my document, it doesn’t seem to be saved, for when I open the document again, the style is NOT applied (numbering style). Any ideas ?
EDIT
Here’s a screencast showing the possible bug.
Libreoffice 6.1
Linux mint 17 Qiana
The document is an odt file.
You should make a screenshot of what you expect list to look like and how ti looks like after reopening. This way you intrigue more people.
@Kruno thanks for the pro-tip, the screencast is at : LIbreoffice 6.1, list style is lost after quitting. on Vimeo
The only way I found to reproduce the problem was to fiddle with the “list” toolbar button.
I first created a paragraph style with list property (linked to a built-in list style). I typed a few paragraph in the current paragraph style. I selected those paragraphs and applied my custom paragraph style with list property (like your List Contents). I then changed the numbering from the toolbar button drop-down menu.
Considering it is only an experiment, I transferred the change into the list style so that it becomes permanent. To make things more demonstrative, I chose a different numbering than the one from the button. Applied, saved, reopened.
The list displays with the toolbar formatting.
Remember that whenever you play with toolbar buttons, you create direct formatting. What is worse is that bullet/numbering changes cannot be removed with Format>Clear direct formatting. The golden rule is whenever you style your document, never use again direct formatting because there are non obvious interactions between styles and direct formatting. The first of which is precedence of D.F. over styles.
To recover from the situation:
Format>Clear direct formatting
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Great explanation thanks a million for the extra special care to write a comprehensive answere. Indeed, when I open the document and place the cursor on the liste paragraphes, the numbering toolbar is in its “active” state (it is pressed). I will try the recipe and get back to you.
@ajlittoz tried your reciepe but it didn’t solve my issue, screencast available here : list style's not saved on Vimeo
But starting from a blank page I can confirm that working with styles from the beginning (and not with the toolbar buttons) will save the list style 
!
Don’t know if it is related: you modify your list style in Numbering Style tab. I don’t like these tabs (and don’t trust them either) because they set various parameters in the last two tabs Position and Customize which are the only ones to consider. Using the other tabs after starting customizing in the two last ones usually causes conflicts and needs retuning.
Anyway, this doesn’t explain why mods are not saved.
Have you tried modifying the list style before applying the change to the paragraphs?
Thank. You. So. Much. The problem was with the Character Style applied to the List 1 style when done through the Numbering Style tab. When done with Customize it is persistent ! see : lo6liststyleisntsaved-solved on Vimeo
LO is supposed to fit beginners’ and power users’ needs. For the former, many shortcuts to higher features are offered, like the Numbering Style tab in list styles. Shortcuts will then set several (many?) parameters in various configuration sections to give supposed “universal” results. But as you noted, these shorcuts create a mess if you started customising your styles manually. Never mix both methods. Once you move away from direct formatting (i.e. when you begin to feel at ease with styles), play only with manual custom configuration, never again trust the shortcuts.
In case of list styles, stick with Position and Customize tabs, none other.
I changed saving my doc from docx to doc ie word 97-2003 solved issue ! Idents are saved and tab to indent works!
Always save in native ODF format, i.e. .odt .
See [Tutorial] Differences between Microsoft and AOO/LO files