Now that we have autotiling for tilemaps (which is fantastic btw.) I think it would be a good thing to extend this feature into the runtime. Oftentimes you may want to do changes on the tilemap at runtime that would require this option or you end up having to autotile manually by also adjusting the adjacent tiles accordingly.
Or in my case, I´m loading levels from an array and if I could just add a bunch of walls and have the autotiling take over from there, that would be great. Right now I´ll have to define corners and such manually. (As a sidenote, I have reasons for not loading it from an exported tilemap json)
I can see it either as it´s own set of actions "set tile at X with brush Y" or as an addition to the existing "set tile" actions (of course including the option to not use an autotile brush)