Binder was an extremely useful extension to “accrete” documents of common purpose. It disappeared from Office 2003, - Microsoft again doing its couldn’t care thing.
There have been many requests for alternatives, but none are specific enough, or are too expensive to consider.
The modern “Document Management Systems” do not really suffice, as many of them make it very difficult to add documents that are already created.
Please give it consideration.
If you are using the term “extension” to imply a new core component, then please refer to this thread. In this case, you are free to raise an enhancement bug to indicate the desired functionality, however be aware that the existing Insert > Object > OLE Object… is likely to be considered similar. If you do raise a bug (none have been raised that I can find) please include as much detail as possible and be sure to mark your report as an “enhancement” and report the corresponding bug number back here in the format “fdo#123456”.
If by “extension” you mean a third-party product such as those on the Extensions website then this is really a matter for any third-party wanting to implement such functionality. You or anyone else is free to work on this, although it may require a detailed understanding of the UNO API or other internal workings of LO.
@oweng - does it sound to you like OP’s wish is met by LO’s master document facility?
I see that the MS Binder feature seemed to allow for incorporating both docs and spreadsheets, for example, and I don’t know whether this is possible for a “Master Doc” in LO.
Still, @ropateviliame - it might be worth looking at some information about using a “master document” (e.g., PDF documentation, or this how-to, or the master-document tag on this site) and see if that meets the need.
@dajare, Binder is an OLE v2.0 feature that allowed objects of differing type to be included in a single document (OBD), thus more like Insert > Object > OLE Object…. It is probably not even worth raising an enhancement request as the functionality is available through other means, which is why MS discontinued it. I will go back and edit my answer.