Tiny bugs:
1. Need to unlock recipes for users who load your mod after researching combinators. You can handle it in on_configuration_changed
2. Not sure if it is only me but pressing E does not confirm the changes

Suggestions:
1. Toggle on-off should probably happen immediately like in a real constant combinator
2. Multiple items like in LTN Combinator Modernized
3. Buffer Combinator doesn't sound right to me, a buffer gives me an impression that it is something to combat fluctuating signals or reduces signal spikes. Suggest Stack Constant Combinator/Stack Multiplier Combinator?

I'll take a look into this today.

Could you be more specific about reproduction steps for the first issue? I used this mod first in a game where I already had combinators, and a quick test with Editor Extensions gave me the buffer combinator.

Could you be more specific about reproduction steps for the first issue? I used this mod first in a game where I already had combinators, and a quick test with Editor Extensions gave me the buffer combinator.

Repro steps for locked recipe issue:
1. Start a map without Buffer combinator mod.
2. Unlock tech until combinators.
3. Save game.
4. Enable Buffer combinator mod.
5. Load the game - user will not be able to craft buffer combinator, even though the tech is unlocked.

You can do a "is tech unlocked for force? -> unlock recipe for force" step in the on_configuration_changed handler to react to migration and tech modification due to startup configuration changes.