Error in creating Dynamic Link

On Line 6 field link is used and on Line 7 Dynamic link is used to add link to the line 6.
Another doctype for Category is already created, what’s the issue?

You needn’t use dynamic link for this purpose. Dynamic link is only useful if the underlying DocType to be linked needs to be changed dynamically. In your case, the Category DocType seems to be a constant.

What you’re really looking for is setting a filter for the sub_category based on the category_type field. Read the documentation to understand how to do this.

Thanks @snv for help, solve that using Link field and some script.

Below I have mentioned the solution that works for me. In case it helps someone:upside_down_face: