No, Marvin doesn't have Gantt charts. Marvin is built for personal planning rather than team project timelines, so this has not been prioritized even when it can also be useful for personal productivity.
But with the Planning Ahead feature you can plan projects for specific weeks and months and see when you'll work on what, that can offer a similar benefit.
Alternatively you can also assign start dates and end or due dates to projects. A start date means a project will be on the backburner until the start date and an end date is like a soft version of a due date (deadline).
Plan projects for a week, month or quarter
With Planning Ahead you can plan tasks and projects for a specific week, month or quarter. Press P to open the planner and switch between the week, month and quarter views. This gives you a rough timeline of what you want to tackle when, and helps you spread your projects out. See Planning Ahead and Capacity planning for weeks, months and quarters.
Give projects a start and an end
Start Dates: hide a project or task until the day you want to start it.
End Dates: set when you want to be finished.
Due dates (deadlines): the date something must be done by. A project's deadline is shown on its tasks too.
Put your work in order
Dependencies: a task waits until another task is done.
Sequential Projects: only the next task in a project shows, so you work through it step by step.
See your weeks
Week Scheduler: drag tasks onto the days of the week.
Calendar: see your tasks, events and time blocks on a calendar.
If a Gantt chart is important to you, let us know, so we can see how many people would use it.