How to set focus on input element dynamically when leaving from the value help dialog

Dear,

I did a demo to illustrate this issue. Could you please have a look?

For example, there are a lot of fields on the screen and they have the value help dialog.
My question is how to set focus on input element dynamically when leaving from the value help dialog?

I did some research, it can use ‘ref’. But what I concern is if there are a lot of fields, do I have to specify the ref one by one?
And the 2nd question is, if there are a lot of ref under vm.$refs, will it impact the performance?

Thanks a lot for your support!