we have already showen it can be slowed down and speed up, as well as quantum atoms being in two different places at the same time as well as all the theorised stuff.
That's not evidence of a dimension but an observed effect, where as space is a dimension we can move within.
The theory that time is a dimension doesn't make sense, there is only ever the present or rather simply space and stuff moving and changing state, stuff runs at different speeds in certain situations but is just some quantum effect, the past and future don't exist.