This chapter is a collection of notes about the current evolution of Therion, and open problems.
In the distribution there is a file with the “todo” list of the features to add to therion:
Other items are on a wish-list (”would be nice to have”):
There are similar lists for  xtherion, and there are annotaions  for the internals of the program (not in english).  The file  TODO.M refers to  The Therion Book, and is not in english.  Finally the file  TODO.SM (also not in english) ...  
When the cave is small, it would be nice to have both plan and extended elevation on the same pdf page. Here is the author’s reply:
I am just not sure, how this should be done. I see only one way:
> This I can imagine, but I am not sure, whether this is what you asked for.
In any case - we will open cross-sections sooner or later. I am currently > working on new 3D generation algorithm and for this, we will definitely need > exact positions of cross sections in 3D. So discussion and suggestions are > welcome.
 area
 Wookey (2005-08-17) pointed out some problems wit hareas.  Infact (M. Budaj) the use of areas should be reduced to a minimum,  and replaced, whenever possible, with point symbols.  
(subtype value)
 If is advisable to avoid areas splitted on two scraps.  In that case one should put one area on each scrap, with a straight  invisible border line (option “-subtype invisible”) [thwiki 17]  where the scrap ends, but there would still be coloring problems  (for instance coloring the map with “altitude”).  This notwithstanding, in caves with several pools and mud banks, areas  splitted on two scrap are almost inevitable.  
Another problem happens when you split a line which is part of the  border of an area. The two new lines get new ids, while the area  still contains the id of the old line (which does not exists any more).  Therefore when the project is compiled with  therion, there is an  error like (here “l14-480–196” is the old id)   
      object does not exist -- l14-480--196
  
  A little help comes from  xtherion: clicking on the error, it brings up  the map editor with the problem causing area selected.  You must go to the “Area control” to check the lines on the border of  the area, and find that id.  Unfortunately  xtherion does not highlight the area in the canvas  and it is not so easy to find the other lines of the border, and to  fix the problem.  
Another possibility is to search the id with the text editor open on the file listed on the error line.
The problem is that a graphical item, the id of which is referred by another  item, is dropped leaving a dangling reference.  This is a problem with  xtherion, which should use reference counting  techniques to keep into account the number of references to the  objects. At a minimum  xtherion should give a warning about deleting  a referenced object ...  
join (.th command)
 Probably a similar problem occurs with the “join” command.  In this case the work of  xtherion would be more difficult  because a “join” connects item from different files, and the  “join” appears in a file at a higher (logical) level.  xtherion needs to have this higher-level file open to find  whether the deleting item occurs in a “join”.  
Another problem is the “Show area” command of the “Area control”. It is useful, but it seems that it shows only the lines of type “border”, and not those of type “wall” or “contour”.
 It would be nice if  xtherion interact with a PDF viewer to provide  a view of the exported pdf (map or atlas).  
This is not very disturbing, because right now one can have two windows,  one for  xtherion and the other for the PDF viewer, and switch between  them to visualize the output after the  therion processing.  
Using  xpdf one could have a tighter integration of the viewer with  xtherion. The viewer could be spawned by  xtherion with  the command “xpdf -remote nome_server file.pdf”.  In this case, if there is no  xpdf server running, a new instance of  the program is executed. On the other hand, if there is one, this is  passed a command to open and load (or reload) the requested PDF file.