You cannot.  You have to use project-relative paths.

If you need to transfer the referred file to another place,  you can do it using the Dependency Manager panel's  Relocate function.

Or if the files are already moved by an external tool  you can use the Replace Path function of the Dependency Manager  (on multiple files at once as well).

And can't simple use the following ./ to make the software understand that is this the root of project folder

There is no "current" project strictly saying. Editor will highlight the project that contains the currently active xcomp, but you can mix files from different projects. (although we don't recommend it, except the "Common" project)
But using project relative path is super easy.
Here is an example:
[MyProject]:textures\a.jpg

This is the root of a project:
[MyProject]:

When you are insert a file that is under a project the path will automatically project relative.
So in most cases you don't have to bother with it, everything will automatically behave correctly.