Buttons, or Hyperlinks - Can I Link To A File Location

Why not just keep all the separate files merged into one PDF. Then you won't have the problem of the file path can't follow the thumb drive path.

The buttons can easily be set to jump to the pages within the whole document.

While there may be a way with scripting in Acrobat to accomplish, I will offer this alternative method.

This will require using Acrobat, multiple PDFs and attachments. For each of the categories that you want files to appear in a folder, create a separate PDF. For example "spec sheets" will be a separate PDF. In spec sheets.pdf, attach the external files. In the Attachment panel, select "Show attachments by default". When spec sheets.pdf opens, it will display a list of all the attachments, similar to a folder.

Attachments in a PDF can be any type of file, and can be opened through Acrobat with a prompt. But the user will need an application capable of opening the specific file.

Repeat for other categories, DWG files, revit files, etc.

Create a master PDF that you will now attach all of the category PDFs (spec sheets, DWG, revit). The master PDF can have buttons to navigate to each of the category PDFs, and also link to the attachments if desired.

The master PDF can be duplicated to a thumb drive, which will contain all the external attached files.