If you don't know the administrator email address you have to do the regular account recovery procedure for Google accounts but you might have an additional option that is to demonstrate the domain ownership. For details see Reset your administrator password
How do I recover my Google account (or Gmail) password or username?
Why doesn't G Suite ...
I wrote an enormous set of code to go through every slide and look through every page element.
Table of Contents will be based on the first (in order of addition to the slide) text found. If a text box was intended to be the title but was added later than something else with text it will not be used.
I have not written code to handle grouped page ...