Thank you for your attention.
So it's not possible. If I understood you correctly (English is not my language).
Correct, it is not possible. Except of course with alternative techniques, as mentioned by TRon or as a library.
The whole point of the unit system in Pascal is to modularize the code. You can read up on the concept here:
https://en.wikipedia.org/wiki/Modular_programmingBut to me that article doesn't really explain the technical reason why your requirement of folding a sub unit into a unit is not considered smart.
As an example, lets consider a unit A, which uses unit B. Then a main program uses both unit A and unit B. After compilation the following object files would be created if combining units as early as possible: A (containing a copy of B), B, program. Here the code for B would be repeated in A, inflating the size of A. It seems beneficial because object A contains all the code it requires, but it leads to wasted space. There are two copies of the code for B, which is a waste of space.
Another way to look at it - if unit B contains code that is only ever used by unit A, there is no point in splitting the code into two units. If unit B contains code that can be called by any other unit/program, it doesn't make sense to combine the units early, since it could lead to code duplication and wasted space.
An alternative idea would be to create a library, which can be seen as a collection of units compiled into a single file. Of course this library usually stays a separate file, except when using static linking. But this could also lead to code duplication if unit A is used both in the library and the program linking to the library (at least I think so, not checked).