Variable field name in create object with fields

[jbshcrack]

I’m a newbie to Thunkable, and working for my school project.
I’m using Firebase, to store and manage data, but I have to make a directory name variable. But the “Create object with fields” block does not support it. How to solve this problem?
What I want to make is shown in the picture.

[actech]

You need to create empty object and to use a different block