Please add a feature that you can allow subprojects (maybe up to three levels).

The Plus-/Minus-Sign, e.g. when you add conditions for a filter, are confusing. One might think that "+" is a positive condition and "-" is a negative condition (if the condition is not met, then the task will be shown). Maybe you can use other symbols or change the layout a bit.

Schedule: You tell Doit.im for instance that you have 2 hours and 30 minutes time. Then it can suggests you a list of possible tasks (which fit into that time frame). But you can also do changes to that suggestions (similar to "Plan").