AnotherCrappyDM
Explorer
The generator doesn't really do that for you. If you got some new +1 armor or a +1 weapon, for example, it will need to be added to the Start page as a base item and then change the bonus to the appropriate place, and also added to your inventory sheet (for weight cauculations). Other items will need to be added to the inventory sheet, and any stat changes will have to be manually changed, like is necessary for the Ioun Stone of Strength. A Ring of Protection would need to be added as armor (other), and add a +1 to all 6 saves, as well as adding it to your inventory. To do all of this with just one action would require using macros, and those are actively being avoided (for compatibility reasons, I believe).
Also, if you loose your magic item (say a green slime eats your Ring of Protection, or perhaps you were at ground zero when a meteor swarm hit and your ioun stone was destroyed!), you will need to undo any changes made regarding that item, just as you did when you added it to your character sheet. The generator does most of the math for you, but it does not automate the details of magic items.
Automating magic items can be done with or without macros. The real problem is the volume of items. The CS has over 1000 items built in and many of them have unique properties. The manhours to put all these in are beyond my commitment to this. Also, without using macros, the number of formulas required would be immense and would lag excel with frequent recalculations.
The problem with using macros is (besides mobile/tablet compatibility) they have to be written very precisely to account for shifts in cell locations as the tool matures. A formula in a cell will automatically update if columns/row are added/moved where as a macro can't update explicit cell references. Compounding the issue.. magic items can be removed which means we'd have to set up change events in the macros and these would fire every time users made changes to specific areas of the workbook (inventory sheets, weapon/armor slots, gear slots) and have to check ALL of the magic items to figure out what to update (and we'd have to write all that scripting and update it with every major revision/publication.
TL;DR version - Implementing magic items is a messy proposition regardless of method.