NotePlan shows @mentions in its sidebar. However, it doesn't (yet) allow hiding of ones with the same start, so every different @start(date), @EnD(date) etc. get shown, making the list hard to navigate.
I could try changing @start(date), @Due(date) etc. to @start/date etc. to save polluting the list, but still giving enough structure to allow my automatic processing.
However, this then deviates further from TaskPaper format, which is probably undesirable.