It's always helpful to post the macro itself.
File > Export > Export Macros.
As you read on, you'll notice that I wrote the remainder of this post before I saw your reply. Regardless, you can adjust the actions each key combo performs to suit your needs. In this case, you'd just simulate ⌥Tab.
It crossed my mind that you might be insisting on holding one key while you press another because you want different held keys to make the same trigger do different things.
For example:
Press key A, = Tab
Hold key 1, press key A = ⌥Tab
Hold key 2, press key A = ⌘Tab
Hold key 3, press key A = ⇧ Tab
That's the only reason I could think that someone might want to do that rather than simulate hotkeys with their own modifiers.
In the macros below, I've used hotkey triggers for clarity, but you'll replace them with USB Device Key triggers. Leave the macros disabled until your triggers are set up.
X-Keys Hold.kmmacros (23 KB)
Replace the Hotkey triggers with the USB Device Key triggers that you'd like to hold in order to make another key do different things. Enable this macro and the red action and press one of the keys. You'll see its TriggerValue appear in a window. Copy this, ready to paste into the second macro below. (Disable the red action again until you want to get another hold key TriggerValue.)
X- Keys - A-B-C Switch for Held Keys.kmmacros (48 KB)
Open up one of the "Do different things when different keys are held" groups and paste the previously copied TriggerValue into one of its Switch fields.
Repeat until you've set up all the hold keys you'd like and then adjust the red actions to do whatever you'd like them to. Set the triggers to the USB Device Keys you intend to press (while another is held), enable the macro and away you go...