Does "levels" mean "depth"? To give the feel how deep in the subject you are?
Don't stacked "parents" give that feel?
Yes! Level means depth.
> Don't stacked "parents" give that feel?
No! The stack doesn't give me that feel, because visually, it doesn't look like a stack. My brain perceives a series of plain text lines as a block of information. There's a reason we add symbols (numbers, discs) to checklists. We want them differentiated from normal text blocks. Of course you don't necessarily need to use symbols, you could also make use of relative positioning (between levels) or color (varying the intensity of the same color as you move up and down the levels, or use a color theme), etc.
Regards!
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Will check closer that transparency feature you talk about.
Thank you!