I played with invokeai and liked it quite a bit, but it didn't even let me recall my last prompt (so keeping a prompt history would be loads better).

The only way to do that I know of is to right click and select 'use prompt' from an image you generated.

wow, that's a start, thanks!

As Invoke is open-source and already has transformers as a dependency, it should be pretty easy to add.

Discussing with the maintainers on their discord now :) https://discord.com/channels/1020123559063990373/10201235598...

I miss when such discussion happened in Github issues

You're preaching to the choir!