Manuel Domínguez 

I'm a a bit confused by this question so forgive me if the answer I provide is not really your problem.  When you say "pop-up window" are you referring to this one?

If you are then the answer would be that what you see here is correct.  This will never have a list of previously used termbases.  It offers you a selection of the available types of terminology resources and when you select one, such as the one you have highlighted in this "pop-up window" you will then be provided with an interface that allows you to select the termbase you're looking for.

So I don't see a problem here.

However, if what you really mean is why aren't the termbases you used before already selected, then this would be because you added them to your project settings and not as a default selection through File -> Options or as part of a project template you have defined.  Projects can all b different so each project has its own unique settings.  Perhaps this article, or some of the ones linked at the end will be helpful to understand this concept?

https://multifarious.filkin.com/2014/01/24/those-project-settings/

Hi Paul! Thank you so much for your response. Let me clarify you what happened:

The "pop-up window" I referred to was actually the one it is shown on the second screenshot I included on my first post. Here's the thing: I had previously created a termbase for a file I wanted to translate. When I clicked on the option shown on the screenshot you included in your reply, I was taken to the interface in which you can select the existing termbases. The termbase that I had previously created couldn't be found there even though I could see it using Windows File explorer and not the Trados interface. 

In the past, I was able to add a termbase to a new project by selecting the option you showed me on your screenshot. But now, I don't know why the TB isn't shown to be selected even though it already exists. You can check this on the second and third screenshot I included on my original post.

Thanks for your help!

Manuel Domínguez 

ok - now I see what you're getting at, thanks for clarifying.

Assuming these are the same folders, as the paths are not completely clear, I think the problem is most likely related to the use of OneDrive.  It looks like some sort of synching problem to me.

I think that if you copy all these termbases into a folder that is not being managed by OneDrive that you won't have this problem.

Manuel Domínguez 

ok - now I see what you're getting at, thanks for clarifying.

Assuming these are the same folders, as the paths are not completely clear, I think the problem is most likely related to the use of OneDrive.  It looks like some sort of synching problem to me.

I think that if you copy all these termbases into a folder that is not being managed by OneDrive that you won't have this problem.

Thanks for your prompt reply! I'll let you know what happened once I have tried your suggestion. 

Hi Paul! It seems it worked. I still have to check whether it worked for the TM because though I could see it appearing to be selected when moved to another location, the TM wasn't filled while translating the text. I will have to repeat the process with another file to see if it works fine for the TM. 

Now, I've come with another curious situation: the exported translated file cannot be opened. It's a PDF, but I guess that the original format has caused the trouble. I'll check that later by testing another PDF file.

Manuel Domínguez 

Can you create a new thread for the new problem if needed?  It's easer to track and have clear questions and answers when they are separate.  This helps others too.

Manuel Domínguez said:

Now, I've come with another curious situation: the exported translated file cannot be opened. It's a PDF, but I guess that the original format has caused the trouble. I'll check that later by testing another PDF file.

It sounds odd though since Studio does not create PDF translated files.  Under the hood we convert the PDF to DOCX and then the exported file is actually a DOCX.  If you end up with a PDF extension it sounds buggy so maybe try changing the extension to docx and see if it opens then?

If not, definitely create a new thread and we can try to help further.