Mojang disabled candles on not full blocks like chests and enchanting tables. But there still is a way to get candles on them. Here is how it works: first place a block. Then a candle on this block. Remove the block to make the candle float. Now place the not full block under the floating candle. I hope I helped!
greetings
Karljakob
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WAI, see comment on MC-203572

This bug report wasn't about floating candles, it's about candles on not full blocks. It's completly ok if the float (like that) but Mojang disabled candles on not full blocks
Its still the same bug, https://twitter.com/kingbdogz/status/1331641881256730626 shows that it is intended

like I said it's not about floating candles

Mojang clearly doesn't want candles on not full blocks, else they wouldn't have disabled them. It's not even possible to shift r click the not full block with a candle
It's intentional that candles don't need a support block and remain floating after the block they've been placed on has been removed, see MC-203572.