Ideally, ANYTHING you do on a project should be a task/activity. Even when you use the Project Summary Task (Format Tab, far-right checkbox) and enable Task 0, everything rolls-up to this activity (a.k.a. the project). In theory, these to-do’s should be activities on the schedule (Gantt Chart view), even if they’re 15 minutes. However, at some point, you could end-up micro-managing your project.
I have two options to offer.
(1) If your organization uses Project Server, then if/when you upload the project and publish it, the project site for the project COULD have Project Server ‘Tasks’ enabled. These ‘tasks’ are NOT the same as the activities in the MS Project file (schedule). These are nothing more than a simple SharePoint list that you could leverage to track these to do’s. Perfect use for this as I have done. If/when you create a Project-site task, anyone on the project with authorization, can see these, update them. This is a great way to increase communications within the team.
(2) The other option is to create a custom view and use one custom field. I first copied the Gantt Chart view to one called ‘To Do view’. Then, I hid the Activity and Duration columns. I then added the Text1 field but renamed it to ‘To Do’. I then created a filter to only display ‘activities’ in this view that have something in the Text1/To Do column (non-blank). So at this point, if I switch views to the To Do view, I only see ‘to do’ tasks. I believe this might be what you need but I caution your use for these reasons. Any of these ‘to do’ activities, to MS Project, are still legit activities. They just look like ‘to do’ activities to you. Therefore, if any of them have a date further out than any of the other activities, your project will appear to be later also. Any time/effort you put to these ‘to do’ will increase your project’s actual work, actual money spent, etc. Use this option with caution.