A special thanks to the Vinu Shmup X account for posting this tip. I always had a feeling the Konami code had to be in use somewhere within Gradius Origins. I tried a few places myself and did not succeed. Vinu Shmup showed us exactly where. Executing the code correctly will unlock you an additional game (maybe two, but I only unlocked one when I tried). I can confirm the code works on the Nintendo Switch and the Steam PC version.
The code in case you need a reminder is
⬆️⬆️⬇️⬇️⬅️➡️⬅️➡️🅱️🅰️ START (start may not be required)
Do it on Salamander’s version selection screen to unlock the Salamander Power-Up Capsule version. That’s a completely new game that’s a mix between Salamander and the Japanese Life Force– uses the Salamander art and color scheme, but the Life Force power-up capsules.
Thanks, I’ll try again later. I must have done something wrong, as it didn’t work for me.