I'm not sure what your exact use case and requirements are, but I'll share some general thoughts below. I also strongly encourage you to post in the HubSpot Ideas Forum to see if there are other users looking for the same functionality.
Otherwise, here are some HubSpot tools worth checking out:
HubSpot Projects — this seems like it's the closest to what you're asking for, though it does require a Professional HubSpot subscription. Projects allow you to set tasks, sub-tasks, timelines, and details (where you could include the link to the respective deal record)
HubSpot Tickets — I've seen clients use tickets to track and manage project status. Paired with HubSpot tasks, you could create ticket stages for your main project milestones and automatically create and assign tasks accordingly with a Professional HubSpot subscription. Tickets can also be associated with deals, so that should make for easy access (here's a quick HubSpot Academy ticket walkthrough as well)
HubSpot Tasks — while these may not be a standalone solution, they'll likely be useful to you as you're assigning project to-dos. Tasks can be associated with contact, company, and deal records as well, so you can easily access those records and tie completed actions back to them