I am looking for suggestions to keep a master list in sync with a sub-listing which has sub-tasks.

I have a master project list with associated demographics (budget, PM, function, start, end, implement, etc). Leadership would like to identify some of these project for presentation in a high-level gannt. But not really a gannt. just the milestones and "go-live" dates as well as key meeting dates. Additionally, leaders will be augmenting the sub-list with additional "steps" which will not be maintained in the master list.

The sub list only needs these fields to accomplish the objective:

Project (this is field to keep in sync with master)

SubTask (manual input to add detailed sub-tasks to Project)

Function (ownership, eg retirement team, international, etc)

Category (meeting, milestone, launch)

Start month (first month) and End month (last month) - these will usually be the same

Currently, I am exporting master project list to excel, deleting unwanted projects, adding sub-tasks, and manually highlighting appropriate months with category symbols. Very manual and very time consuming.

My objective is to create a secondary Smartsheet which stays in sync with the Master project list so that any change in the master updates the secondary Smartsheet without losing what is already there. Everything except for the subtasks should be updated as changes are made in the master.

Any suggestions would be much appreciated.