Currently, blocks used to upgrade a modular machine are shown in JEI preview in the vertical list on the right, and you can click them to highlight them in the structure. However, you (1) aren't really able to press "R"/"U" on these upgrade blocks in the JEI preview and (2) searching for the upgrade block's usages does not bring up the Structure Preview tab like other materials used in the machine.
So keeping the click functionality to highlight the upgrade blocks is good, but I suggest:

1. Allow button input (show recipes, show usages, bookmark buttons) on the SlotItemVirtualSelectables of the upgrade ingredients
2. When just normally searching usages in JEI search for an upgrade block, have it show the appropriate usage in the Structure Preview tab.

I know the upgrade blocks show as a cycling ingredient in the list of preview blocks in the bottom row(s), where you can use normal JEI functions on it there, but it would be nice to have the same functionality on the vertical list of upgrade ingredients.

Seems to be working!