Hmmm... clearing forest... not other benefit than the one you have already mentioned (I suppose one could be modded in, not sure though)

Hmmm... demolish building...

One scenario occurs to me... If I build the unique faction Tower of Dominion, in my main city. But no longer need it in that city, I cannot build one in another city, so I can demolish this building and build it in another city...

Maybe you built slums just for the growth bonus, but once your city is level 5, you demolish the slums so as to not incur the penalty to unrest anymore (as the growth bonus is not as vital in such a city)

I'm sure I can think of a few others, but not very many.

Clear forest helps you move around in your own areas better.  Whenever I play without Master Scouts, I usually do it to every possible space after I build a lumber mill.

Also as he said, I have deleted buildings from conquered AI cities in order to be able to snake with them before as well if there were closeby resources not inside the walls.

As Crastiloowa said, the borders of your city don't change if you delete a building, so it can allow you to snake really far...  I consider this way too exploity to use on purpose, but at times I have defeated an AI city with spell victory towers built which got deleted with the walls remaining in place.  In those times I didn't re-fill that space before extending further off of it.

If you don't care about such things, you can do some really really powerful things with the delete buildings command.

Wait a second, demolish building will alllow me to get lumbermills into cities that's settled one tile away from forests?

No... the demolish building will not actually do that. But my snaking mod will allow you build lumber mills on cities that are more than 1 tile away from forests.