Had planter fasciatis early 2021 with morning heel pain stabbing in nature. gone eventually. but dull heel ache returns if i do moderate/intense activity (4+ miles walking/3+ hrs standing) after sitting down post activity. how to resume activity?

You didn’t mention what was required to provide you with relief of plantar fasciitis. Obviously it helped but it did not take care of the problem completely. I would take the next step whether that be changing your shoes for more support or seeing a podiatrist and getting either over-the-counter supports or a custom-made orthotic. All of these are viable Options.