Clarify docs on controlling compound documents

[nattyg93]

Fixes #

Description of the Change

Checklist

• PR only contains one change (considered splitting up PR)
• [n/a] unit-test added
• documentation updated
• [n/a] CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[codecov]

Codecov Report

Merging #579 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #579   +/-   ##
=======================================
  Coverage   95.64%   95.64%           
=======================================
  Files          55       55           
  Lines        2850     2850           
=======================================
  Hits         2726     2726           
  Misses        124      124

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[sliverc]

👍 Thanks.