Agreed. Knowing which variables are in which flows, and being able to filter on a variable across flows - this would take VF a step closer to achieving a more “design while you develop” experience.
FYI: As a workaround, I do this manually with a (meta) flow I call “Workbench” (see attached), where I group multiple related flows into a single block for reference only. A block can represent anything across flows: a skill version, a feature within a skill, a group of related variables, a single variable, etc. It allows me to update features or variables without making mistakes and forgetting to update dependent flows. It’s not the best solution, but I find it’s more readily actionable than documenting with text, and more reliable than using my working memory alone.