I'll go down the list, sorted into categories based on my knowledge and opinion:

Parks mapped as parks, to stay as parks: 
Bala Cynwyd Park, Gen'l Wayne Park, Amherst Field, Narberth Park, Narbrook Park, McMoran Park, Eco Valley Nature Park, Rolling Hill Park, Mill Creek Valley Park, Gladwyne Park, Ashbridge Park, Penn Wynne Park, Wynnewood Valley Park, South Ardmore Park, Vernon Young Park, Austin Park, Shortridge Park, Merion Botanical Park, Margaret Braun Hill (location needs adjustment), Pencoyd Park (by Greentree Ln), Sabine Park, West Mill Creek Park, Flat Rock Park, Waner Ave Park, Packer Park, Linwood Park, Merion Gateway Park, Wynnewood Station Park, Bala Ave. Park, Cynwyd Station Park, Cynwyd Heritage Trail Space, and Gulley Run Park ( segments which touch Bryn Mawr Ave).

Other spaces in the township currently mapped as parks, nature preserves, et al -- either I do not know how to tag or know little about:
Kenealy Nature Park, Henry Lane Park and Garden, Saunders Woods, Idlewild Farm, Black Rock Road Site, Williamson Road Site, Harriton Park, Appleford Estate, Riverbend, Indian Creek Basin Park, Sharpe Bird Sanctuary

Other publicly open spaces mapped in the Township: 
Stoneleigh, Wheeler/Harriton Farms Woods, https://www.openstreetmap.org/way/471302992 

Other areas I believe are incorrect or missing:
Lewis J Smith Park (encompassing pool and roller hockey, separated from McMoran Park by the hill), Righters Mill Road Site (currently mapped as encompassed by Gulley Run Park, should be mapped the same as Williamson/BR sites), Merion Square Rd Site (missing, same qualifications), Fuller Tract?

We still need to discuss Pencoyd Park and where it deserves to be mapped. It is signed by Greentree Rd, and that is where it is according to LM Parks (https://www.lowermerion.org/departments/parks-and-recreation-department/township-parks). I just feel like the other three areas that were mapped deserve to be tagged as something. 
(Note character limit)