2. Is it possible (by a keyboard-shortcut) to execute all blocks of a session
starting from top to down? Sometimes I make small changes here and there and I
just like to say o.k. tangle all this together and execute it, refresh and
show me all new results. This might be even combined by a org-mode variable
which allow to define which results need to be refreshed before saving the org-
mode file (something like #+EXECBYSAVE: name_of_session).
I press C-x C-s rather frequently without much thinking of it. If I want make
sure that e.g., all generated output files (e.g. figures) are in sync with the
code it would be nice to say C-x C-s  and all external figures will be
recreated if necessary.

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