All Autocomplete is an ST3 plugin that I first thought was sort of a gimmick, but turns out to very useful. Normally automatic autocompletion (meaning not coming from snippets or autocompletion files) uses words only in the currently-open document. All Autocomplete uses all open documents.
A disadvantage, however, is that it includes words with three characters or more which, for my taste, clutters up the popups. But this minimum is directly in the plugin code, not a preference-file.
To increase this value from three to five, first extract them with the PackageResourceViewer plugin (or just unzip it…
*.sublime-package files are just renamed zip files). This creates the directory
C:\Users\jeffy\AppData\Roaming\Sublime Text 3\Packages\All Autocomplete\
In that directory, open
all_views_completions.py and change
MIN_WORD_SIZE = 3
MIN_WORD_SIZE = 5
This directory overrides the package file. You could also re-zip this back into the file, and delete the directory.
The bad thing about this setting being directly in the code, instead of in a configuration file, is that this change must be made each time AllAutocomplete is updated.