Help needed with subtree export

[Alain . Cochard]

I only recently discovered subtree export, which I thought would be
better suited for me, but I have trouble to switch.

Consider the following file:

   #+SELECT_TAGS: export conditional
   #+EXCLUDE_TAGS: 

   #+OPTIONS: toc:nil title:nil author:nil date:nil tags:nil

   * I  :export:
   ** 1
   ** 2
   ** nth
   *** conditional :conditional:
   * II

If I use 'C-c C-e l o', I have everything under '* I' exported. If I
transfer 'conditional' from '#+SELECT_TAGS:' to '#+EXCLUDE_TAGS:', I
have everything under '* I' except the '*** conditional' headline.
This is want I want: be able to selectively include/exclude the
headlines with the ':conditional:' tag by simply transferring
'conditional'.

Now, if I use 'C-c C-e C-s l o' on '* I', it gives the same as above
when 'conditional' belongs to '#+EXCLUDE_TAGS:' but, after the
transfer of 'conditional' to '#+SELECT_TAGS:', only the '** nth'
headline is exported.

Is there a convenient way to achieve my goal?  Sure, I can put an
':export:' tag on '** 1', '** 2', and '** nth', but it is not very
practical.  I can also introduce a 'fake' headline and subtree export
it instead:

   * fake
   ** I :export:
   *** 1
   *** 2
   *** nth
   **** conditional :conditional:
   * II

but I don't like this workaround either.

Thanks in advance


PS: I have a minor comment about the manual: when reading the following

   ‘SELECT_TAGS’
        The default value is ‘("export")’.  [...]

   ‘EXCLUDE_TAGS’
        The default value is ‘("noexport")’.  [...]

I find it difficult to anticipate what will happen when there is no
tag at all.

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