I wish to change the default spacing and style of the outline numbering options, such that when I click the icon in the menu, I have the desired effects in my document. So, is this possible, and how to do?
Not sure if I understand your question.
Remember that all formatting issues in LO are controlled by styles. You are encouraged to read the Writer guide to learn the basis.
“Outline numbering” paragraphs, by default, are associated with Heading 1 to Heading 9 paragraph styles. Modifying these styles allows you to set spacing, margins, font, size … to your liking.
The numbering itself is defined by the Tools → Outline Numbering... dialog. If you want the number set differently from the heading text (colour, font, size, …), this is possible by selecting a character style instead of None and customising it.
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