Hello there, and first let me explain that I am an Affinity Designer 'Noob' so forgive me if my suggestion is naive! (Be gentle with me LOL)...
Isometrics seem such a popular design/illustration function and certainly (most sorry to mention the 'opposition') Procreate seems to be motoring ahead with adding additional isometric functionality... So I wonder if an Isometric projection tool set is concievable?
I used to have a third party gadget for Adobe Illustrator that did this, a small pallet that automated the traditional '86%/30o/-30o' (etc...) projection, with a button for left, right and top projections.