In LibreOffice v6.2.3.2 Writer, if I create a custom paragraph style with a list style attached, I have the following problem. If the paragraph style has an area color set, then the different levels of the list shift the area color left edge to the right. Is this a bug?
This is not a bug: the paragraph area is a rectangular area: horizontally between the leftmost (for LTR) of the two of indents: [before text; first line] and the right indent; vertically covering area of all the paragraph lines. The numbering controls the indents of the paragraph, potentially changing the indents depending on the list level - thus changing the (colored) paragraph area.
You are welcome to come with an enhancement request to the bug tracker - but you need to make sure your proposal makes sense in the multitude of usage scenarios, not giving to unexpected results or ambiguities - the most difficult task in any proposal.