is it theoretically possible to have cooling paste be jelly like? so it just returns to previous position after cooling down? or its just to irrelevat problem to invest in it?
There are thermal pads that perform equally or better than thermal pastes, due to their design. In particular, something like https://thermalmanagement.honeywell.com/us/en/products/therm... can be better than a good thermal paste like https://www.thermal-grizzly.com/en/products/16-kryonaut-en. The thermal conductivity is improved due to the use of a phase shifting material. Reliability is improved due to the fact that it will naturally return to solid without cracking during heat cycling.
That is already available and used in some Laptops. Look up Honeywell thermal pad.
The problem is as always, cost.