Is it possible to merge memory in webhook with new properties?

Hi,

if I send this to the chatbot:

{"conversation":{"memory":{"username":"bob"}}}

it will replace the actual memory.

I tried this but it didnt work.

{"conversation":{"memory":{"username":"bob"},"merge_memory":true}}

is it possible to merge only with the API? Or is this also possible in the webhook?

Best regards

Philipp