While planning in a story, if you need to add a new member, then you can enter new dimension members directly into the data table. However, you can't create members for Account, Version, or Date dimensions from a data table.
While you can create members in a story, you can't delete them. Members can only be deleted from the model or public dimension (assuming they don't have any posted values).
Add a New Dimension Member from a Story
When you right-click on a call and choose Add Member, a blank row is inserted below.

You enter in the new member into the new blank row. In the following example, you can see that Sweatshirts is added.
An input help allows you to access a dialog to select the Parent Node and input the Description and ID. You can choose to define the new member as a child or sibling of existing members.

Note
If the dimension has properties, you can input existing or new property values as well.Insert Unposted Member
When a dimension is set to display posted values, the Add Member option is used to add a new row, for example. By double-clicking the cell, you can insert an unposted member. This allows you to add members (that don't have data in the fact table) to the input form and input values.
Unbooked Data
When you create a new member, it won't have any data. A member with no data is referred to as Unbooked and is displayed as a dash - in the table cell.
Unbooked data isn't visible unless the Unbooked Data setting for the table is turned on. To add new members more quickly, the Unbooked Data setting is turned off by default. However, if you create a new member on an inner dimension, then Unbooked Data is turned on automatically for that member.

Save a New Member
After you save the new member, you are no longer able to change the member details.
Note
Master Data: At an enterprise level, you must decide where master data is to be maintained. In general, a corporate repository (master data governance) approach is taken. However, in some cases, adding new dimension members while planning in a story is feasible, for example, it is feasible when planning for a consumer products company to add new products as and when needed.