Received this answer from  Dan MacKinnon (Overleaf Product Specialist)

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Hi Tejas,

Maintaining a project for your bibliography, and then sharing this with other projects is generally a good practice, but I can appreciate how your large bibliography project can become hard to manage. 

Here's some advice that may help make this more manageable.

In your "master bibliography" project, include a .tex file that prints out the whole bibliography (using \nocite{*}) in an organized way. This allows you to (1) ensure that your bib entries are compilable, and (2) provides you with an easier to read reference.

In this example of a master bibliography, I've done a few things to help: https://www.overleaf.com/read/tmgbwgmyvjgn

1. I used bibLaTeX, because this allows for easy sorting options. 

You can do this even if you don't use bibLaTeX in the projects that ultimately use the bibliography, or you can adapt the approach described here to use natbib or bibTeX instead.

An example of the sorting you can do with bibLaTeX is 
\printbibliography[heading=bibintoc, type=book, title={Books}]

This just prints out the books in the bibliography, based on the "type=book". The option bibintoc, makes sure that the reference list is added to the table of contents at the start of my document.

See here: https://www.overleaf.com/learn/latex/Bibliography_management_with_biblatex

2. You can split up your .bib files logically within your master bib project.

In this case I've separated out "technology" citations, but in principle you could break up your bib in whatever logical way makes sense.

\addbibresource{masterbib.bib}
\addbibresource{technology.bib}

I find that this helps keep the "master bibliography" manageable. You may identify some other ways of organizing things that are helpful to you.

There are a few tricks required in this approach if you want to be sure you are printing everything. For example, if you want to print out more than one type in a group you may want to define a "bibfilter" that covers it. You may also need to be aware of some odd behaviour - the APA biblatex processes "incollection" as "inbook", so you will see that is what is used as the "type" in this example.

If you try this approach, you may need to check out relevant posts on Stack Exchange to help with problems that you run into, or read the documentation on your particular choice of bibliography management software.

With this kind of approach, you can manage your bibliography directly in an Overleaf project, rather than using separate reference management software.

You may want to view the "Working with Bibliographies" webinar recording here: https://www.overleaf.com/events/webinars, or check out the other bibliography related help pages on our website: https://www.overleaf.com/learn.

Hope this helps.

Best,

Dan

  **Advice from Overleaf**

One convenient way to set this up if you’re planning to use the same files across multiple projects is to organize things as follows:

-  Create a “master” project containing your common files e.g.  .bib, .cls, .sty, graphics, etc.  
- In your “child” projects, click the “Add file” button at the top of the project side bar.  
- Select “File from other project”, and navigate to your “master” project,  and select the file that you need.  
- You will now be  able  to use the linked file in your “child” project.

If  you’ve  modified  the  original  copy  of  the  files  in  the  “master”  project,remember  to  right-click  on  the  linked  .bib  in  the  “child”  projects  and  then“Refresh”  (or  click  on  the  file  and  click  on  the  Refresh  button  in  the  file preview  that  appears),  to  pull  in  the  changes.   
[Can I share files (e.g. .bib and some graphics) across my projects?](https://www.overleaf.com/help/226-can-i-share-files-e-dot-g-bib-and-some-graphics-across-my-projects.W5qHGd0zbCI)

Let's call our master bib file *yashraj.bib*.

 **How to use Use**
 
 Whenever  you  need  to  include  a  reference  in  your  article,  
- Go  to  yashraj.bib.
-  Press  command  +  F  or  Ctrl  +  F  to  find  the  article  corresponding  to  your search string.  
- If found, copy the bib label.  
- In your project refresh yashraj.bib and use it in the cite command.
- If this fails see the reference list in the PDF of this project and see if you hit upon anything.  

You may download it and do the same press command +F or Ctrl + F thing. 

All entries are arranged alphabetically according to the author in the PDF.

**How to Maintain**

Before adding a bibentry search it in yashraj.bib, etc as above to see if it already exists. 
To add a bibliographic entry to this project 

- Search it on web (e.g google,  etc) and copy bibtex information from google scholar,  semantic scholar,  etc. or from [Well-maintained BibTeX Databases](https://tex.stackexchange.com/q/131917/129388)

- check the entry for the most common errors [software-generated-bibliographic-entries-common-errors-and-other-mistakes-to-check](https://tex.stackexchange.com/questions/386053/software-generated-bibliographic-entries-common-errors-and-other-mistakes-to-ch)  (thanks @samcarter)

- Add the biblabel to the table. The biblabel must be of the format firstauthoryearfirstwordoftitle or more easily first author year first word of the title. Example paola2012quantum.

- Recompile this project whenever you add a bib entry.
- Convert the month to a no. For example dec is converted to 12 
- Fix errors as soon as they appear.