Currently, when you select Deep Delve, the left space is always locked out, because Deep Delve is not allowed for level 50.
It should make sense to enable there Deep Delve at level 100, for players who have progressed past 100, with starting treasure multiplier x1.5 .
This would mainly help mid-game players so that they can comfortably progress while still allowed to do a Deep Delve at a lower level at their convenience.