Traveling From India to Barbados - outside India's air-transport bubble [closed]

Per the guidelines you yourself link to, bubble flights to the UK are supposed to be for:

Any Indian national holding any type of valid UK visa and destined for UK only.

If you do not hold a visa for the UK, you will thus not be allowed to board. Even if you do hold a UK visa, you may experience problems if your itinerary indicates you're only transiting instead of being destined to "UK only".

However, if you do have a UK visa that allows multiple entries, I don't see anything that would stop you from booking one India-UK "bubble" roundtrip and nesting a UK-Barbados roundtrip within that. It's not clear to me if you're supposed/"allowed" to do this, but that's a separate question.

All that said, given how difficult travel continues to be these days, I suspect you would find it much easier and cheaper to travel to a tropical bubble destination like the Maldives or the Seychelles instead, since both can be reached on direct flights and travel to both is 100% permitted.