The two forms amount to the same result; this is a general approach in all interfaces: sometimes the action accomplished is communicated to the user by means of a noun (here “mise”) and sometimes by means of the corresponding verb (here “mettre”). There is no rule for using one rather than the other; which is used is determined only by the preference of each developer; most often, they insist on some consistence and they use only one of the two possibilities, at least in some parts of their interfaces.

So, as it should probably have been understood from the above, there is no question of tenses but only a matter of usage involving either a substantive or a verb.

mise en forme: formatting

mettre en forme: (to) format

mettre sous form de: convert into