To access the documents easier, you can create hierarchy categories and link the documents to the related categories.

to get more information about Document Categories see "Document Category🔗". 

Add document to a Category

To add the opened document to a category, click on the button from the action bar, and find the categories you need,

Select them by making the checkbox on the first column checked, and at the end click on the button.

Remove the document from a Category

To remove the document from a category, select the category from the list first, click on the button,  if you are sure about it, click on a  button.

Go back to the documents list

If you need to go back to see the list of the documents you can click on the button from the right side of the action bar.