As the title says, I’m looking for recommendations for a task management app - primarily this is to help me with my prioritisation of different tasks. I work in accountancy and deal with multiple clients at once. I’m perfectly fine tracking my time and getting on with a task (so don’t need time blocking features) but find it challenging after finishing a task to identify the best thing to do next.

The “necessary” features I’m looking for are:

• Works on Windows and Android and syncs between them (including syncing between multiple Windows computers). My work uses Windows and my work phone is an Android phone, and I need to use them to keep my work and personal life separate. I also use a desktop when working from the office but have a laptop to work from home, and I need to be able to access the application on both.
• Can generate a project (or at least a task list) from a template. Much of my work is required to follow fixed steps, in order to ensure compliance. Having to create these checklists manually is too onerous to be practical.
• Nested projects/tasks
• Priority setting for tasks
• Setting deadlines and have subsequent task deadlines dependent on the completion of other tasks
• A defer option to push back the start date/deadline of tasks or projects
• Reminders and alerts
• Set certain tasks to recur. This so I can remind myself to do my timesheet, set an out of office for my non-working days etc.

In addition the following would be desirable

• App based rather than having a web interface. This way I won’t get distracted by other tabs I have open.
• Adding information/notes to the highest level of a project. I like to have some notes on a clients available to me and adding information in a note feels logical
• Being able to temporarily hide/deprioritise tasks that can’t currently be progressed. Often what tasks I can do depend on a client providing me additional information, a review being done etc. Therefore I would like to be able to push tasks onto a sort of backburner while this is happening
• Colour coding of tasks/projects based on deadline or stage
• Setting a context for different tasks, so I can separate client related work and administrative items
• Generating tasks from emails
• An API so I can tailor some functionality (if I need to)

I don’t mind paying for an application if it does what I need, but the variety of available task managers is overwhelming and it’s hard to identify which one will actually do all the things I need it to! Some suggestions I’ve seen on other posts are Marvin, Workflowy, Omnifocus (using the web interface for windows), and MyLifeOrganised. Would any of these do what I need them to do?