So my main question is this. From all the readings i can see you could paint a door on the outside of the dome of the tiny hut spell and then go into it? A PC asked me this and i cant see why it cant work. Marvolous pigments only says it needs to be painted onto a surface, never does it say it has to be non magical.
So can you paint a door onto a tiny hit and enter it if the hut isnt yours?

All other creatures and objects are barred from passing through it. Spells and other magical effects can’t extend through the dome or be cast through it.

That's a quote from Tiny Hut and it seems very clear that no - you could paint on the surface but no magic or anything can get through the hut.

So if you painted on the surface to make the surface see through and not opaque, the magic effect wouldnt be extending through the dome itself. That should work by the way its worded.

Sure you could maybe make it transparent - but it wouldn't help you get inside. The dome would still be there and still bar all entry.

I don't think [Tooltip Not Found] would even let you see inside either. Depends on whether the DM considers turning the dome transparent as an effect extending through the dome.