When creating Matrix Items, you can create templates for sets of attributes/dimensions that you use frequently e.g. clothing or shoe sizes. You can then apply these templates to matrix items when you create them, saving you time when creating similar or related item ranges.
1) In the main menu in the Back Office, expand the Items heading, then click on Matrix Templates:

2) Click on New in the top left:

3) Give the template a name and click Save.

4) Click on the template you just created in the grid. A Template Components grid will appear either below the Templates grid, or to the right of it (depending on the size and shape of your screen).

5) Click on New in the top left and populate the first attribute and code fields, then click on Save.

When you have created the first attribute and code, you will need to click New to create the next attribute, and so on.
6) To apply a template, go to the Child Items tab on the item record and click the Apply Template button next to the dimension you want to apply it to. Find the required template in the drop-down list, then click Apply Template.

The attributes from the template will be applied to that dimension. From here we can delete any attributes we do not wish to create by clicking on the red cross next to them, or add more manually using the blue + icon.

If the wrong template has been selected, you can remove it by clicking on the red rubbish bin icon next to it.
This technique can save a lot of time. For example, if you create a template with sizes XXXS to XXXL, you can recall the template and delete any attributes that are not applicable to the matrix you are working upon, rather than manually entering all of the attributes that you do need.
For more help with Matrix item creation, please read through the following articles:
How do I create a Matrix item?
Understanding Matrix Attributes and Best Practice for Matrix Creation