If you have DRS Power Ops (Bicycle Bundle, RMS Toolkit, Matrix Master), matrix editing tools are included. Otherwise follow these instructions.
If you need to change a dimension for a specific item, such as the size or color, you will need to edit the individual item code.
Locate the item code, bring up Item Properties, and modify the main description, then click on M under Member of: and update the dimension entries in the table for that item.
You will need to update the base description, dimensions in the matrix, as well as the subdescriptions listed under the General tab.
If you need to change information on all matrix items, such as Type, cost, category, price, etc., locate the master code for your matrix item (type=M), double-click to view Item Class Properties, then click on Attributes.
All editable fields for that matrix group are listed in white. Scroll to the right to see them all. You can also edit the main description for an individual item from this screen.
Note: Option 2 is available within Option 1 if you click on the M first, then Attributes.
TIP: If you need to change an entire row in Attributes, change the first entry, then right-click and select Copy, then right-click again and select Paste to All Rows.