Mmmmmm.
But i am thinking more in the lines of the selectable dashboards manner instead of a drop down list.
Give this one a go.
- Fill user lists and button names in BDM preset.
- Select tab User and select one of the 4 user lists (1 = default)
- Use button USER to open and button CLOSE to manage the charts.
- More than 8 users symbols navigate buttons will appear.
- The last selected user list will stay active under the button USER.


Ps. You could have made a 32 pair user list grouped by 8 charts and use the navigate buttons to switch between the 4 groups.